.. comment: -*- fill-column: 72; mode: rst; -*- =============================== Package polexpr documentation =============================== 0.5.1 (2018/04/22) ================== .. contents:: Basic Examples -------------- The syntax is:: \poldef polname(x):= expression in variable x; where: - in place of ``x`` an arbitrary *dummy variable* is authorized, i.e. per default any of ``[a-z|A-Z]`` (more letters can be declared under Unicode engines.) - ``polname`` consists of letters, digits, and the ``_`` and ``'`` characters. It must start with a letter. .. attention:: The ``'`` is authorized since ``0.5.1``. As a result some constructs recognized by the ``\xintexpr`` parser, such as ``var1 'and' var2`` will get misinterpreted and cause errors. However these constructs are unlikely to be frequently needed in polynomial expressions, and the ``\xintexpr`` syntax offers alternatives, so it was deemed a small evil. Of course the ``\xintexpr`` parser is modified only temporarily during execution of ``\poldef``. One can also issue:: \PolDef{polname}{expression in variable x} which admits an optional first argument to modify the variable letter from its default ``x``. ``\poldef f(x):= 1-x+x^2;`` defines polynomial ``f``. Polynomial names must start with a letter and may contain letters, digits, underscores and the right tick character. The variable must be a single letter. The colon character is optional. The semi-colon at end of expression is mandatory. ``\PolDef{f}{1-x+x^2}`` does the same as ``\poldef f(x):= 1-x+x^2;`` To use another letter than ``x`` in the expression, one must pass it as an extra optional argument to ``\PolDef``. Useful if the semi-colon has been assigned some non-standard catcode by some package. ``\PolLet{g}={f}`` saves a copy of ``f`` under name ``g``. Also usable without ``=``. ``\poldef f(z):= f(z)^2;`` redefines ``f`` in terms of itself. ``\poldef f(T):= f(f(T));`` again redefines ``f`` in terms of its (new) self. ``\poldef k(z):= f(z)-g(g(z)^2)^2;`` should now define the zero polynomial... Let's check: ``\[ k(z) = \PolTypeset[z]{k} \]`` ``\PolDiff{f}{f'}`` sets ``f'`` to the derivative of ``f``. The name doesn't have to be ``f'`` (in fact the ``'`` is licit only since ``0.5.1``). .. important:: This is not done automatically. If some new definition needs to use the derivative of some available polynomial, that derivative polynomial must have been defined via ``\PolDiff``: something like ``T'(x)^2`` will not work without a prior ``\PolDiff{T}{T'}``. ``\PolDiff{f}{f''}`` obtains second derivative. ``\PolDiff[3]{f}{f'''}`` computes the third derivative. :: $f(z) = \PolTypeset[z]{f} $\newline $f'(z) = \PolTypeset[z]{f'} $\newline $f''(z) = \PolTypeset[z]{f''} $\newline $f'''(z)= \PolTypeset[z]{f'''} $\par .. important:: The package does not currently know rational functions: ``/`` in a parsed polynomial expression does the Euclidean quotient:: (1-x^2)/(1-x) does give ``1+x`` but :: (1/(1-x))*(1-x^2) evaluates to zero. This will work as expected:: \poldef k(x):= (x-1)(x-2)(x-3)(x-4)/(x^2-5x+4); .. _warningtacit: .. attention:: ``1/2 x^2`` skips the space and is treated like ``1/(2*x^2)`` because of the tacit multiplication rules of \xintexpr. But this means it gives zero! Thus one must use ``(1/2)x^2`` or ``1/2*x^2`` or ``(1/2)*x^2`` for disambiguation: ``x - 1/2*x^2 + 1/3*x^3...``. It is even simpler to move the denominator to the right: ``x - x^2/2 + x^3/3 - ...``. It is worth noting that ``1/2(x-1)(x-2)`` suffers the same issue: xint_ tacit multiplication always "ties more", hence this gets interpreted as ``1/(2*(x-1)*(x-2))`` which gives zero by polynomial division. Thus, use one of ``(1/2)(x-1)(x-2)``, ``1/2*(x-1)(x-2)`` or ``(x-1)(x-2)/2``. After:: \poldef f_1(x):= 25(x-1)(x^2-2)(x-3)(x-4)(x-5);% \poldef f_2(x):= 37(x-1)(x^2-2)(x-6)(x-7)(x-8);% the macro call ``\PolGCD{f_1}{f_2}{k}`` sets ``k`` to the (unitary) GCD of ``f_1`` and ``f_2`` (hence to the expansion of ``(x-1)(x^2-2)``.) ``\PolToExpr{k}`` will (expandably) give in this case ``x^3-x^2-2*x+2``. This is useful for console or file output (the syntax is Maple- and PSTricks-compatible; the letter used in output can be (non-expandably) changed via a redefinition of `\\PolToExprVar`_.) ``\PolToExpr*{k}`` gives ascending powers: ``2-2*x-x^2+x^3``. Examples of localization of roots --------------------------------- .. attention:: At ``0.5``, `\\PolToSturm{P}{S} `_ was modified to create a chain of primitive integer coefficients polynomials. This speeds up evaluations, hence localization of roots afterwards. Thus ``S_1`` will not necessarily be the derivative of ``S_0``, even if ``P`` is square-free. - To make printed decimal numbers more enjoyable than via ``\xintSignedFrac``:: \renewcommand\PolTypesetOne[1]{\PolDecToString{\xintREZ{#1}}}% ``\PolDecToString`` will use decimal notation to incorporate the power of ten part; and the ``\xintREZ`` will have the effect to suppress trailing zeros if present in raw numerator (if those digits end up after decimal mark.) Notice that the above are expandable macros and that one can also do:: \renewcommand\PolToExprCmd[1]{\PolDecToString{\xintREZ{#1}}}% to modify output of `\\PolToExpr{polname}`_. - For extra info in log file use ``\xintverbosetrue``. - To make producing this documentation simpler, the results from execution of the code snippets are not included. Please try them out yourself... A typical example ~~~~~~~~~~~~~~~~~ In this example the polynomial is square-free; we can make sure of that by comparing the degree of the first element of the Sturm chain with the degree of the original polynomial. In such case the second element of the Sturm chain is still the polynomial first derivative, because there was no further reduction. :: \poldef f(x) := x^7 - x^6 - 2x + 1; \PolToSturm{f}{f} \PolSturmIsolateZeros{f} The \PolTypeset{f} polynomial has \PolSturmNbOfIsolatedZeros{f} distinct real roots which are located in the following intervals: \PolPrintIntervals{f} Here is the second root with ten more decimal digits: \PolRefineInterval[10]{f}{2} \[\PolSturmIsolatedZeroLeft{f}{2}`_. As a side effect the function ``polname()`` is recognized as a genuine ``\xintexpr...\relax`` function for (exact) numerical evaluation (or within an ``\xintdefvar`` assignment.) It computes values not according to the original expression but via the Horner scheme corresponding to the polynomial coefficients. .. attention:: Release ``0.3`` also did the necessary set-up to let the polynomial be known to the ``\xintfloatexpr`` (or ``\xintdeffloatvar``) parser. Since ``0.4`` this isn't done automatically. Even more, a previously existing floating point variant of the same name will be let undefined again, to avoid hard to debug mismatches between exact and floating point polynomials. This also applies when the polynomial is produced not via ``\poldef`` or ``\PolDef`` but as a product of the other package macros. See `\\PolGenFloatVariant{polname}`_. The original expression is lost after parsing, and in particular the package provides no way to typeset it. This has to be done manually, if needed. .. _PolDef: ``\PolDef[letter]{polname}{expression in letter}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Does the same as `\\poldef `_ in an undelimited macro format (thus avoiding potential problems with the catcode of the semi-colon in presence of some packages.) In absence of the ``[letter]`` optional argument, the variable is assumed to be ``x``. .. _PolGenFloatVariant: ``\PolGenFloatVariant{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Makes the polynomial also usable in the ``\xintfloatexpr`` parser. It will therein evaluates via an Horner scheme with coefficients already pre-rounded to the float precision. See also `\\PolToFloatExpr{polname}`_. .. attention:: Release ``0.3`` did this automatically on ``\PolDef`` and ``\poldef`` but this was removed at ``0.4`` for optimization. Any operation, for example generating the derivative polynomial, or dividing two polynomials or using the ``\PolLet``, **must** be followed by explicit usage of ``\PolGenFloatVariant{polname}`` if the new polynomial is to be used in ``\xintfloatexpr`` or alike context. .. _PolLet: ``\PolLet{polname_2}={polname_1}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Makes a copy of the already defined polynomial ``polname_1`` to a new one ``polname_2``. Same effect as ``\PolDef{polname_2}{polname_1(x)}`` but with less overhead. The ``=`` is optional. .. _PolGlobalLet: ``\PolGlobalLet{polname_2}={polname_1}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Acts globally. .. _PolAssign: ``\PolAssign{polname}\toarray\macro`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Defines a one-argument expandable macro ``\macro{#1}`` which expands to the (raw) #1th polynomial coefficient. - Attention, coefficients here are indexed starting at 1. - With #1=-1, -2, ..., ``\macro{#1}`` returns leading coefficients. - With #1=0, returns the number of coefficients, i.e. ``1 + deg f`` for non-zero polynomials. - Out-of-range #1's return ``0/1[0]``. See also `\\PolNthCoeff{polname}{number}`_. The main difference is that with ``\PolAssign``, ``\macro`` is made a prefix to ``1 + deg f`` already defined (hidden to user) macros holding individually the coefficients but `\\PolNthCoeff{polname}{number}`_ does each time the job to expandably recover the ``Nth`` coefficient, and due to expandability can not store it in a macro for future usage (of course, it can be an argument in an ``\edef``.) The other difference is the shift by one in indexing, mentioned above (negative indices act the same in both.) .. _PolGet: ``\PolGet{polname}\fromarray\macro`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Does the converse operation to ``\PolAssign{polname}\toarray\macro``. Each individual ``\macro{number}`` gets expanded in an ``\edef`` and then normalized via xintfrac_\ 's macro ``\xintRaw``. The leading zeros are removed from the polynomial. (contrived) Example:: \xintAssignArray{1}{-2}{5}{-3}\to\foo \PolGet{f}\fromarray\foo This will define ``f`` as would have ``\poldef f(x):=1-2x+5x^2-3x^3;``. .. note:: Prior to ``0.5``, coefficients were not normalized via ``\xintRaw`` for internal storage. .. _PolFromCSV: ``\PolFromCSV{polname}{}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Defines a polynomial directly from the comma separated list of values (or a macro expanding to such a list) of its coefficients, the constant term being the first item. No validity checks. Spaces from the list argument are trimmed. List items are each expanded in an ``\edef`` and then put into normalized form via xintfrac_\ 's macro ``\xintRaw``. Leading zero coefficients are removed:: \PolFromCSV{f}{0, 0, 0, 0, 0, 0, 0, 0, 0, 0} defines the zero polynomial, which has only one (zero) coefficient. See also expandable macro `\\PolToCSV <\\PolToCSV{polname}_>`_. .. note:: Prior to ``0.5``, coefficients were not normalized via ``\xintRaw`` for internal storage. .. _PolTypeset: ``\PolTypeset{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~ Typesets in descending powers in math mode. It uses letter ``x`` but this can be changed via an optional argument:: \PolTypeset[z]{polname} By default zero coefficients are skipped (issue ``\poltypesetalltrue`` to get all of them in output). These commands (whose meanings will be found in the package code) can be re-defined for customization. Their default definitions are expandable, but this is not a requirement. .. _PolTypesetCmd: ``\PolTypesetCmd{raw_coeff}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Checks if the coefficient is ``1`` or ``-1`` and then skips printing the ``1``, except for the constant term. Also it sets conditional `\\PolIfCoeffIsPlusOrMinusOne{A}{B}`_. The actual printing of the coefficients, when not equal to plus or minus one is handled by `\\PolTypesetOne{raw_coeff}`_. .. _PolTypesetOne: ``\PolTypesetOne{raw_coeff}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The default is ``\xintSignedFrac`` but this macro is annoying as it insists to use a power of ten, and not decimal notation. One can do things such as for example: [#]_ :: \renewcommand\PolTypesetOne[1]{\num{\xintPFloat[5]{#1}}} \renewcommand\PolTypesetOne[1]{\num{\xintRound{4}{#1}}} where e.g. we used the ``\num`` macro of ``siunitx`` as it understands floating point notation. .. [#] the difference in the syntaxes of ``\xintPFloat`` and ``\xintRound`` is explained from the fact that ``\xintPFloat`` by default uses the prevailing precision hence the extra argument like here ``5`` is an optional one. One can also give a try to using `\\PolDecToString{decimal number}`_ which uses decimal notation (at least for the numerator part). .. _PolTypesetMonomialCmd: ``\PolTypesetMonomialCmd`` ^^^^^^^^^^^^^^^^^^^^^^^^^^ This decides how a monomial (in variable ``\PolVar`` and with exponent ``\PolIndex``) is to be printed. The default does nothing for the constant term, ``\PolVar`` for the first degree and ``\PolVar^{\PolIndex}`` for higher degrees monomials. Beware that ``\PolIndex`` expands to digit tokens and needs termination in ``\ifnum`` tests. .. _PolTypesetCmdPrefix: ``\PolTypesetCmdPrefix{raw_coeff}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Expands to a ``+`` if the ``raw_coeff`` is zero or positive, and to nothing if ``raw_coeff`` is negative, as in latter case the ``\xintSignedFrac`` used by `\\PolTypesetCmd{raw_coeff}`_ will put the ``-`` sign in front of the fraction (if it is a fraction) and this will thus serve as separator in the typeset formula. Not used for the first term. .. _PolTypeset*: ``\PolTypeset*{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~ Typesets in ascending powers. Use e.g. ``[h]`` optional argument (after the ``*``) to use letter ``h`` rather than ``x``. .. _PolDiff: ``\PolDiff{polname_1}{polname_2}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This sets ``polname_2`` to the first derivative of ``polname_1``. It is allowed to issue ``\PolDiff{f}{f}``, effectively replacing ``f`` by ``f'``. Coefficients of the result ``polname_2`` are irreducible fractions (see `Technicalities`_ for the whole story.) .. _PolDiff[N]: ``\PolDiff[N]{polname_1}{polname_2}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This sets ``polname_2`` to the ``N``-th derivative of ``polname_1``. Identical arguments is allowed. With ``N=0``, same effect as ``\PolLet{polname_2}={polname_1}``. With negative ``N``, switches to using ``\PolAntiDiff``. .. _PolAntiDiff: ``\PolAntiDiff{polname_1}{polname_2}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This sets ``polname_2`` to the primitive of ``polname_1`` vanishing at zero. Coefficients of the result ``polname_2`` are irreducible fractions (see `Technicalities`_ for the whole story.) .. _PolAntiDiff[N]: ``\PolAntiDiff[N]{polname_1}{polname_2}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This sets ``polname_2`` to the result of ``N`` successive integrations on ``polname_1``. With negative ``N``, it switches to using ``\PolDiff``. .. _PolDivide: ``\PolDivide{polname_1}{polname_2}{polname_Q}{polname_R}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This sets ``polname_Q`` and ``polname_R`` to be the quotient and remainder in the Euclidean division of ``polname_1`` by ``polname_2``. .. _PolQuo: ``\PolQuo{polname_1}{polname_2}{polname_Q}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This sets ``polname_Q`` to be the quotient in the Euclidean division of ``polname_1`` by ``polname_2``. .. _PolRem: ``\PolRem{polname_1}{polname_2}{polname_R}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This sets ``polname_R`` to be the remainder in the Euclidean division of ``polname_1`` by ``polname_2``. .. _PolGCD: ``\PolGCD{polname_1}{polname_2}{polname_GCD}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This sets ``polname_GCD`` to be the (monic) GCD of the two first polynomials. It is a unitary polynomial except if both ``polname_1`` and ``polname_2`` vanish, then ``polname_GCD`` is the zero polynomial. .. ``\PolIGCD{polname_1}{polname_2}{polname_iGCD}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ **NOT YET** This **assumes** that the two polynomials have integer coefficients. It then computes the greatest common divisor in the integer polynomial ring, normalized to have a positive leading coefficient (if the inputs are not both zero). ``\PolIContent{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~ **NOT YET** This computes a positive rational number such that dividing the polynomial with it returns an integer coefficients polynomial with no common factor among the coefficients. .. _PolToSturm: ``\PolToSturm{polname}{sturmname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ With, for example, ``polname`` being ``P`` and ``sturmname`` being ``S``, the macro starts by computing polynomials ``S_0 = P``, ``S_1 = P'``, ..., with ``S_{n+1}`` the opposite of the remainder of euclidean division of ``S_{n-1}`` by ``S_{n}``. .. attention:: Since ``0.5``, it further normalizes all these polynomials by making them primitive (see `\\PolMakePrimitive`_). The last non-zero remainder ``S_N`` is up to a factor the GCD of ``P`` and ``P'`` hence it is a constant (i.e. ``1`` or ``-1`` since ``0.5``) if and only if ``P`` is square-free. In case ``S_N`` is not a constant, the macro then goes on with dividing all ``S_k``'s with ``S_N`` (which then becomes ``1``). Thus ``S_0`` has exactly the same real and complex roots as polynomial ``polname``, but each root being now with multiplicity one. .. _PolToSturm*: ``\PolToSturm*{polname}{sturmname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Does not divide the Sturm chain by its last element. .. _PolSetToSturmChainSignChangesAt: ``\PolSetToSturmChainSignChangesAt{\macro}{sturmname}{fraction}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Sets macro ``\macro`` to the number of sign changes in the Sturm chain with name prefix ``sturmname``, at location ``fraction`` (which must be in format as acceptable by the xintfrac_ macros.) .. note:: The author was lazy and did not provide rather an expandable variant, where one would do ``\edef\macro{\PolNbOf...}``. This will presumably get added in a future release. After some hesitation it was decided the macro would by default act globally. To make the scope of its macro definition local, use ``[\empty]`` as extra optional argument. .. _PolSetToNbOfZerosWithin: ``\PolSetToNbOfZerosWithin{\macro}{sturmname}{value_a}{value_b}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Applies the `Sturm Theorem`_ to set ``\macro`` to the exact number of distinct roots of ``sturmname_0`` in the interval ``(value_a, value_b]`` (the macro first re-orders the value for ``value_a <= value_b`` to hold). .. note:: The author was lazy and did not provide rather an expandable variant, where one would do ``\edef\macro{\PolNbOf...}``. This will presumably get added in future. After some hesitation it was decided the macro would by default act globally. To make the scope of its macro definition local, use ``[\empty]`` as extra optional argument. .. _PolSturmIsolateZeros: ``\PolSturmIsolateZeros{sturmname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ First, it evaluates using `Sturm theorem`_ the number of distinct real roots of ``sturmname_0``. .. important:: The Sturm chain **must** be of the reduced type, i.e. as constructed via `\\PolToSturm{polname}{sturmname}`_. Then it locates, again using `Sturm theorem`_, as many disjoint intervals as there are roots. Some intervals reduce to singleton which are roots. Non-singleton intervals get refined to make sure none of their two limit points is a root: they contain each a single root, in their respective interiors. .. This procedure is covariant with the independent variable ``x`` becoming ``-x``. Hmm, pas sûr et trop fatigué The interval boundaries are decimal numbers, originating in iterated decimal subdivision from initial intervals ``(-10^E, 0)`` and ``(0, 10^E)``; if zero is a root it is always identified individually. The non-singleton intervals are of the type ``(a/10^f, (a+1)/10^f)`` with ``a`` an integer, which is neither ``0`` nor ``-1``. Hence ``a`` and ``a+1`` are both positive or both negative. The interval boundaries (and exactly found roots) are made available for future computations in ``\xintexpr``-essions or polynomial definitions as variables ``L_1``, ``L_2``, etc..., for the left end-points and ``R_1``, ``R_2``, ..., for the right end-points. Also two macro arrays (in the sense of xinttools_'s ``\xintAssignArray``) are created for holding the interval end-points written out in standard decimal notation (see `\\PolDecToString{decimal number}`_). To access these values, macros `\\PolSturmIsolatedZeroLeft{sturmname}{index}`_ and `\\PolSturmIsolatedZeroRight{sturmname}{index}`_ are provided. .. important:: Trailing zeroes in these stored decimal numbers are significant: they are also present in the decimal expansion of the exact root. .. note:: The actual array macros are ``\POL_ZeroIntL`` and ``\POL_ZeroIntR`` but as these names use the non-letter character ``_`` and possibly also digits from ``sturmname``, the accessor macros above have been made part of the package. The start of decimal expansion of a positive ``k``-th root is given by ``\PolSturmIsolatedZeroLeft{sturmname}{k}``, and for a negative root it is given by ``\PolSturmIsolatedZeroRight{sturmname}{k}``. These two decimal numbers are either both zero or both of the same sign. The number of distinct roots is obtainable as ``\PolSturmNbOfIsolatedZeros{sturmname}``. .. note:: In the current implementation the ``...`` variables and the ``\POL_ZeroInt...`` arrays are globally defined. On the other hand the Sturm sequence polynomials obey the current scope. .. note:: When two successive roots are located in adjacent intervals, the separation between them is not lower bounded. See `\\PolRefineInterval*{sturmname}{index}`_. .. note:: As all computations are done *exactly* there can be no errors... apart those due to bad coding by author. The results are exact bounds for the mathematically exact real roots. Future releases will perhaps also provide macros based on Newton or Regula Falsi methods. Exact computations with such methods lead however quickly to very big fractions, and this forces usage of some rounding scheme for the abscissas if computation times are to remain reasonable. This raises issues of its own, which are studied in numerical mathematics. .. _PolRefineInterval*: ``\PolRefineInterval*{sturmname}{index}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The ``index``\ -th interval (starting indexing at one) is further subdivided as many times as is necessary in order for the newer interval to have both its end-points distinct from the end-points of the original interval. This means that the ``k``\ th root is then strictly separated from the other roots. .. _PolRefineInterval[N]: ``\PolRefineInterval[N]{sturmname}{index}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The ``index``\ -th interval (starting count at one) is further subdivided once, reducing its length by a factor of 10. This is done ``N`` times if the optional argument ``[N]`` is present. .. _PolEnsureIntervalLength: ``\PolEnsureIntervalLength{sturmname}{index}{E}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The ``index``\ -th interval is subdivided until its length becomes at most ``10^E``. This means (for ``E<0``) that the first ``-E`` digits after decimal mark of the ``k``\ th root will then be known exactly. .. _PolEnsureIntervalLengths: ``\PolEnsureIntervalLengths{sturmname}{E}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The intervals as obtained from ``\PolSturmIsolateZeros`` are (if necessary) subdivided further by (base 10) dichotomy in order for each of them to have length at most ``10^E`` (length will be shorter than ``10^E`` in output only if it did not change or became zero.) This means that decimal expansions of all roots will be known with ``-E`` digits (for ``E<0``) after decimal mark. .. _PolPrintIntervals: ``\PolPrintIntervals[varname]{sturmname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This is a convenience macro which prints the bounds for the roots ``Z_1``, ``Z_2``, ... (the optional argument ``varname`` allows to specify a replacement for the default ``Z``). This will be done in a math mode ``array``, one interval per row, and pattern ``rcccl``, where the second and fourth column hold the ``<`` sign, except when the interval reduces to a singleton, which means the root is known exactly. The user is invited to renewcommand the macro if some other type of tabular environment for example is wanted. In each array cell the corresponding interval end-point (which may be an exactly known root) is available as macro `\\PolPrintIntervalsTheEndPoint`_ (in decimal notation). And the corresponding interval index is available as `\\PolPrintIntervalsTheIndex`_. These values may be tested to decide some on-the-fly customization (color for example), via the following auxiliaries which can be modified by user. Furthermore these auxiliaries can also use the following conditionals: `\\PolIfEndPointIsPositive{A}{B}`_, `\\PolIfEndPointIsNegative{A}{B}`_, `\\PolIfEndPointIsZero{A}{B}`_. .. _PolPrintIntervalsPrintExactZero: ``\PolPrintIntervalsPrintExactZero`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This is provided to help customize how an exactly known root is printed in the right most column of the array. The package definition is:: \newcommand\PolPrintIntervalsPrintExactZero{\PolPrintIntervalsTheEndPoint}% Recall that this is expanded in an array cell. If for example you want to print in red the third root, known exactly, the macro could make a test for the value of `\\PolPrintIntervalsTheIndex`_ and act accordingly. .. _PolPrintIntervalsPrintLeftEndPoint: ``\PolPrintIntervalsPrintLeftEndPoint`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Package definition is:: \newcommand\PolPrintIntervalsPrintLeftEndPoint{\PolPrintIntervalsTheEndPoint}% .. _PolPrintIntervalsPrintRightEndPoint: ``\PolPrintIntervalsPrintRightEndPoint`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Package definition is:: \newcommand\PolPrintIntervalsPrintRightEndPoint{\PolPrintIntervalsTheEndPoint}% .. _PolMapCoeffs: ``\PolMapCoeffs{\macro}{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It modifies ('in-place': original coefficients get lost) each coefficient of the defined polynomial via the *expandable* macro ``\macro``. The degree is adjusted as necessary if some leading coefficients vanish after the operation. In replacement text of ``\macro``, ``\index`` expands to the coefficient index (which is defined to be zero for the constant term). Notice that ``\macro`` will have to handle inputs of the shape ``A/B[N]`` (xintfrac_ internal notation). This means that it probably will have to be expressed in terms of macros from xintfrac_ package. Example:: \def\foo#1{\xintMul{#1}{\the\numexpr\index*\index\relax}} (or with ``\xintSqr{\index}``) to replace ``n``-th coefficient ``f_n`` by ``f_n*n^2``. .. _PolReduceCoeffs: ``\PolReduceCoeffs{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ About the same as ``\PolMapCoeffs{\xintIrr}{polname}`` (but maintaining a ``[0]`` postfix for speedier xintfrac_ parsing when polynomial function is used for computations.) This is a one-argument macro, working 'in-place'. .. _PolReduceCoeffs*: ``\PolReduceCoeffs*{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This starred variant leaves un-touched the decimal exponent in the internal representation of the fractional coefficients, i.e. if a coefficient is internally ``A/B[N]``, then ``A/B`` is reduced to smallest terms, but the ``10^N`` part is kept as is. Note: if the polynomial is freshly defined directly via `\\PolFromCSV `_ its coefficients might still be internally in some format like ``1.5e7``; the macro will anyhow always first do the needed conversion to strict format ``A/B[N]``. Evaluations with polynomials treated by this can be much faster than with those handled by the non-starred variant `\\PolReduceCoeffs{polname}`_: as the numerators and denominators remain smaller, this proves very beneficial in favorable cases (especially when the coefficients are decimal numbers) to the expansion speed of the xintfrac_ macros used internally by `\\PolEval `_. .. _PolMakeMonic: ``\PolMakeMonic{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~ Divides by the leading coefficient. It is recommended to execute `\\PolReduceCoeffs*{polname}`_ immediately afterwards. This is not done automatically, due to the case the original polynomial had integer coefficients and we want to keep the leading one as common denominator. .. _PolMakePrimitive: ``\PolMakePrimitive{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Divides by the integer content see (`\\PolIContent `_). This thus produces a polynomial with integer coefficients having no common factor. The sign of the leading coefficient is not modified. Expandable macros ----------------- All these macros expand completely in two steps except ``\PolToExpr`` and ``\PolToFloatExpr`` (and their auxiliaries) which need a ``\write``, ``\edef`` or a ``\csname...\endcsname`` context. .. _PolEvalAtExpr: ``\PolEval{polname}\AtExpr{numerical expression}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It boils down to ``\xinttheexpr polname(numerical expression)\relax``. .. _PolEvalAt: ``\PolEval{polname}\At{fraction}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Evaluates the polynomial at value ``fraction`` which must be in (or expand to) a format acceptable to the xintfrac_ macros. .. attention:: Meaning was changed at ``0.4``. Formerly ``\PolEval{P}\At{foo}`` accepted for ``foo`` an expression which was handled by ``\xintexpr``. See `\\PolEval{polname}\\AtExpr{numerical expression}`_. In particular, to use an ``\xintexpr`` user-declared variable (or e.g. the variables as defined by `\\PolSturmIsolateZeros `_) one **must** use the ``\AtExpr`` syntax. .. _PolEvalReducedAtExpr: ``\PolEvalReduced{polname}\AtExpr{numerical expression}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Boils down to ``\xinttheexpr reduce(polname(numerical expression))\relax``. .. _PolEvalReducedAt: ``\PolEvalReduced{polname}\At{fraction}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Evaluates the polynomial at value ``fraction`` which must be in (or expand to) a format acceptable to the xintfrac_ macros, and produce an irreducible fraction. .. attention:: Meaning was changed at ``0.4``. Formerly the evaluation point could be given as an expression. .. _PolFloatEvalAtExpr: ``\PolFloatEval{polname}\AtExpr{numerical expression}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Boils down to ``\xintthefloatexpr polname(numerical expression)\relax``. This is done via a Horner Scheme (see `\\poldef `_ and `\\PolGenFloatVariant{polname}`_), with already rounded coefficients. [#]_ To use the *exact coefficients* with *exactly executed* additions and multiplications, just insert it in the float expression as in this example: [#]_ :: \xintthefloatexpr 3.27*\xintexpr f(2.53)\relax^2\relax The ``f(2.53)`` is exactly computed then rounded at the time of getting raised to the power ``2``. Moving the ``^2`` inside, that operation would also be treated exactly. .. attention:: At ``polexpr 0.3``, polynoms were automatically also prepared for use in floating point contexts. This got dropped at ``0.4`` for optimization purposes. See `\\PolGenFloatVariant{polname}`_. .. [#] Anyway each floating point operation starts by rounding its operands to the floating point precision. .. [#] The ``\xintexpr`` here could be ``\xinttheexpr`` but that would be less efficient. Cf. xintexpr_ documentation about nested expressions. .. _PolFloatEvalAt: ``\PolFloatEval{polname}\At{fraction}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Evaluates the polynomial at value ``fraction`` which must be in (or expand to) a format acceptable to the xintfrac_ macros, and produces a floating point number. .. attention:: Meaning was changed at ``0.4``. Formerly the evaluation point could be given as an expression. .. _PolIfCoeffIsPlusOrMinusOne: ``\PolIfCoeffIsPlusOrMinusOne{A}{B}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This macro is a priori undefined. It is defined via the default `\\PolTypesetCmd{raw_coeff}`_ to be used if needed in the execution of `\\PolTypesetMonomialCmd`_, e.g. to insert a ``\cdot`` in front of ``\PolVar^{\PolIndex}`` if the coefficient is not plus or minus one. The macro will execute ``A`` if the coefficient has been found to be plus or minus one, and ``B`` if not. .. _PolLeadingCoeff: ``\PolLeadingCoeff{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Expands to the leading coefficient. .. _PolNthCoeff: ``\PolNthCoeff{polname}{number}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It expands to the raw ``N``-th coefficient (``0/1[0]`` if the index number is out of range). With ``N=-1``, ``-2``, ... expands to the leading coefficients. .. _PolDegree: ``\PolDegree{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~ It expands to the degree. This is ``-1`` if zero polynomial but this may change in future. Should it then expand to ``-\infty`` ? .. _PolIContent: ``\PolIContent{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~ It expands to the contents of the polynomial, i.e. to the positive fraction such that dividing by this fraction produces a polynomial with integer coefficients having no common prime divisor. See `\\PolMakePrimitive `_. .. _PolToExpr: ``\PolToExpr{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~ Expands [#]_ to ``coeff_N*x^N+...`` (descending powers.) .. [#] in a ``\write``, ``\edef``, or ``\csname...\endcsname``, but not under ``\romannumeral-`0``. By default zero coefficients are skipped (issue ``\poltoexpralltrue`` to get all of them in output). By default, no ``+`` sign before negative coefficients, for compliance with Maple input format (but see `\\PolToExprTermPrefix{raw_coeff}`_.) Also, like the default behaviour of `\\PolTypeset{polname}`_, does not print (for the non constant terms) coefficients equal to plus or minus one. The degree one monomial is output as ``x``, not ``x^1``. Complete customization is possible, see next macros. Of course ``\PolToExpr{f}`` can be inserted in a ``\poldef``, as the latter expands token by token, hence will force complete expansion of ``\PolToExpr{f}``, but a simple ``f(x)`` is more efficient for the identical result. .. _PolToExprOneTerm: ``\PolToExprOneTerm{raw_coeff}{number}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This two argument expandable command takes care of the monomial and its coefficient. The default definition is done in order for coefficients of absolute value ``1`` not be printed explicitely (except of course for the constant term). Also by default, the monomial of degree one is ``x`` not ``x^1``, and ``x^0`` is skipped. For compatibility with Maple input requirements, by default a ``*`` always precedes the ``x^number``, except if the coefficient is a one or a minus one. See `\\PolToExprTimes`_. .. _PolToExprOneTermStyleA: ``\PolToExprOneTermStyleA{raw_coeff}{number}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Holds the default package meaning of `\\PolToExprOneTerm{raw_coeff}{number}`_. .. _PolToExprOneTermStyleB: ``\PolToExprOneTermStyleB{raw_coeff}{number}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ For output in this style:: 2*x^11/3+3*x^8/7-x^5−x^4/4−x^3−x^2/2−2*x+1 issue ``\let\PolToExprOneTerm\PolToExprOneTermStyleB`` before usage of ``\PolToExpr``. Note that then ``\PolToExprCmd`` isn't used at all. To revert to package default, issue ``\let\PolToExprOneTerm\PolToExprOneTermStyleA``. To suppress the ``*``'s, cf. `\\PolToExprTimes`_. .. _PolToExprCmd: ``\PolToExprCmd{raw_coeff}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ It is the one-argument macro used by the package definition of ``\PolToExprOneTerm`` for the coefficients themselves (when not equal to plus or minus one), and it defaults to ``\xintPRaw{\xintRawWithZeros{#1}}``. One will have to redefine it to ``\xintIrr{#1}`` or to ``\xintPRaw{\xintIrr{#1}}`` to obtain in the output forcefully reduced coefficients. .. _PolToExprTermPrefix: ``\PolToExprTermPrefix{raw_coeff}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Defined identically as `\\PolTypesetCmdPrefix{raw_coeff}`_. It prefixes with a plus sign for non-negative coefficients, because they don't carry one by themselves. .. _PolToExprVar: ``\PolToExprVar`` ^^^^^^^^^^^^^^^^^ This expands to the variable to use in output (it does not have to be a single letter, may be an expandable macro.) Initial definition is ``x``. .. _PolToExprTimes: ``\PolToExprTimes`` ^^^^^^^^^^^^^^^^^^^ This expands to the symbol used for multiplication of an ``x^{number}`` by the corresponding coefficient. The default is ``*``. Redefine the macro to expand to nothing to get rid of it (but this will give output incompatible with some professional computer algebra software). .. _PolToExpr*: ``\PolToExpr*{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~ Expands to ``coeff_0+coeff_1*x+coeff_2*x^2+...`` (ascending powers). Customizable like `\\PolToExpr{polname}`_ via the same macros. .. _PolToFloatExpr: ``\PolToFloatExpr{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Similar to `\\PolToExpr{polname}`_ but uses `\\PolToFloatExprCmd <\\PolToFloatExprCmd{raw_coeff}>`_ which by default rounds and converts the coefficients to floating point format. .. note:: It is not necessary to have issued `\\PolGenFloatVariant{polname}`_. The rounded coefficients are not easily recoverable from the ``\xintfloatexpr`` polynomial function hence ``\PolToFloatExprCmd`` operates from the *exact* coefficients anew. Attention that both macros obey the prevailing float precision. If it is changed between those macro calls, then a mismatch exists between the coefficients as used in ``\xintfloatexpr`` and those output by ``\PolToFloatExpr{polname}``. .. _PolToFloatExprOneTerm: ``\PolToFloatExprOneTerm{raw_coeff}{number}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Similar to `\\PolToExprOneTerm <\\PolToExprOneTerm{raw_coeff}{number}>`_. But does not treat especially coefficients equal to plus or minus one. .. _PolToFloatExprCmd: ``\PolToFloatExprCmd{raw_coeff}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ It is the one-argument macro used by ``\PolToFloatExprOneTerm``. Its package definition is ``\xintFloat{#1}``. .. caution:: Currently (xint_ ``1.2p``) ``\xintFloat{0}`` outputs ``0.e0`` which is perfectly acceptable input for Python, but not for Maple. Thus, one should better leave the `\\poltoexprallfalse`_ toggle to its default ``\iffalse`` state, if one intends to use the output in a Maple worksheet. But even then the zero polynomial will cause a problem. Workaround:: \renewcommand\PolToFloatExprCmd[1]{\xintiiifZero{#1}{0.0}{\xintFloat{#1}}} Usage of ``\xintiiifZero`` and not ``\xintifZero`` is only for optimization (I can't help it) because ``#1`` is known to be in ``xintfrac`` raw format. .. _PolToFloatExpr*: ``\PolToFloatExpr*{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Typesets in ascending powers. .. _PolToList: ``\PolToList{polname}`` ~~~~~~~~~~~~~~~~~~~~~~~ Expands to ``{coeff_0}{coeff_1}...{coeff_N}`` with ``N`` = degree (except zero polynomial which does give ``{0/1[0]}`` and not an empty output.) .. _PolToCSV: ``\PolToCSV{polname}`` ~~~~~~~~~~~~~~~~~~~~~~ Expands to ``coeff_0, coeff_1, coeff_2, ....., coeff_N``. Converse to `\\PolFromCSV <\\PolFromCSV{polname}{\}_>`_. .. _PolSturmChainLength: ``\PolSturmChainLength{sturmname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Returns the integer ``N`` such that ``sturmname_N`` is the last one in the Sturm chain ``sturmname_0``, ``sturmname_1``, ... See `\\PolToSturm{polname}{sturmname}`_. .. _PolSturmIfZeroExactlyKnown: ``\PolSturmIfZeroExactlyKnown{sturmname}{index}{A}{B}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Executes ``A`` if the ``index``\ th interval reduces to a singleton, i.e. the root is known exactly, else ``B``. .. note:: ``index`` may be a TeX count, or a ``\value{latexcounter}``, or a numerical expression as parsable by ``\numexpr``: it does not have to be given via explicit digits. This remark applies also to the other package macros with ``index`` being the name of the argument in this documentation. There is also an out-of-range check done for some reasonable error message (right before everything goes haywire). .. _PolSturmIsolatedZeroLeft: ``\PolSturmIsolatedZeroLeft{sturmname}{index}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Expands to the left end-point for the ``index``\ th interval obtained via `\\PolSturmIsolateZeros{sturmname}`_ and possibly refined afterwards. .. _PolSturmIsolatedZeroRight: ``\PolSturmIsolatedZeroRight{sturmname}{index}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Expands to the right end-point for the ``index``\ th interval obtained via `\\PolSturmIsolateZeros{sturmname}`_ and possibly refined afterwards. .. _PolSturmNbOfIsolatedZeros: ``\PolSturmNbOfIsolatedZeros{sturmname}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Expands to the number of real roots of the polynomial ``_0`` (which is the number of distinct real roots of the polynomial used to create the Sturm chain via `\\PolToSturm{polname}{sturmname}`_. .. _PolIntervalWidth: ``\PolIntervalWidth{sturmname}{index}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The ``10^E`` width of the current ``index``\ th root localization interval. Output is in xintfrac_ raw ``1/1[E]`` format (if not zero). Macros for use within execution of ``\PolPrintIntervals`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ More precisely, they can be used within the replacement texts of the `\\PolPrintIntervalsPrintLeftEndPoint`_, etc, macros. .. _PolPrintIntervalsTheEndPoint: ``\PolPrintIntervalsTheEndPoint`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Within a custom `\\PolPrintIntervalsPrintLeftEndPoint`_, custom `\\PolPrintIntervalsPrintRightEndPoint`_, or custom `\\PolPrintIntervalsPrintExactZero`_ this macro expands to the left or right end point of the considered interval. Serves as default replacement for `\\PolPrintIntervalsPrintLeftEndPoint`_ , etc... .. _PolPrintIntervalsTheIndex: ``\PolPrintIntervalsTheIndex`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Within a custom `\\PolPrintIntervalsPrintLeftEndPoint`_, custom `\\PolPrintIntervalsPrintRightEndPoint`_, or custom `\\PolPrintIntervalsPrintExactZero`_ this macro expands to the index of the considered interval. For example if user wants to print the corresponding end points in red, the index value can thus be tested in the replacement text of `\\PolPrintIntervalsPrintLeftEndPoint`_ and the other two similar macros. .. _PolIfEndPointIsPositive: ``\PolIfEndPointIsPositive{A}{B}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Within a custom `\\PolPrintIntervalsPrintLeftEndPoint`_, custom `\\PolPrintIntervalsPrintRightEndPoint`_, or custom `\\PolPrintIntervalsPrintExactZero`_ this macro executes ``A`` if the considered interval end-point is positive, else ``B``. .. _PolIfEndPointIsNegative: ``\PolIfEndPointIsNegative{A}{B}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Within a custom `\\PolPrintIntervalsPrintLeftEndPoint`_, custom `\\PolPrintIntervalsPrintRightEndPoint`_, or custom `\\PolPrintIntervalsPrintExactZero`_ this macro executes ``A`` if the considered interval end-point is negative, else ``B``. .. _PolIfEndPointIsZero: ``\PolIfEndPointIsZero{A}{B}`` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Within a custom `\\PolPrintIntervalsPrintLeftEndPoint`_, custom `\\PolPrintIntervalsPrintRightEndPoint`_, or custom `\\PolPrintIntervalsPrintExactZero`_ this macro executes ``A`` if the considered interval end-point is zero, else ``B``. .. _PolDecToString: ``\PolDecToString{decimal number}`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This is a utility macro to print decimal numbers. It has been backported to xintfrac_ (release ``1.3`` of ``2018/03/01``) under the name ``\xintDecToString``, and the ``polexpr`` macro is simply now an alias to it. For example ``\PolDecToString{123.456e-8}`` will expand to ``0.00000123456`` and ``\PolDecToString{123.450e-8}`` to ``0.00000123450`` which illustrates that trailing zeros are not trimmed. To trim trailing zeroes, one can use ``\PolDecToString{\xintREZ{#1}}``. The exact behaviour of this macro may evolve in future releases of xint_. Booleans (with default setting as indicated) -------------------------------------------- ``\xintverbosefalse`` ~~~~~~~~~~~~~~~~~~~~~ This is actually an xintexpr_ configuration. Setting it to ``true`` triggers the writing of information to the log when new polynomials are defined. .. caution:: The macro meanings as written to the log are to be considered unstable and undocumented internal structures. ``\poltypesetallfalse`` ~~~~~~~~~~~~~~~~~~~~~~~ If ``true``, `\\PolTypeset{polname}`_ will also typeset the vanishing coefficients. ``\poltoexprallfalse`` ~~~~~~~~~~~~~~~~~~~~~~ If ``true``, `\\PolToExpr{polname}`_ and `\\PolToFloatExpr{polname}`_ will also include the vanishing coefficients in their outputs. Technicalities -------------- - The catcode of the semi-colon is reset temporarily by `\\poldef `_ macro in case some other package (for example the French babel module) may have made it active. This will fail though if the whole thing was already part of a macro argument, in such cases one can use `\\PolDef{f}{P(x)} `_ rather. The colon in ``:=`` may be active with no consequences. - As a consequence of xintfrac_ addition and subtraction always using least common multiples for the denominators [#]_, user-chosen common denominators survive additions and multiplications. For example, this:: \poldef P(x):= 1/2 + 2/2*x + 3/2*x^3 + 4/2*x^4; \poldef Q(x):= 1/3 + (2/3)x + (3/3)x^3 + (4/3)x^4; \poldef PQ(x):= P(x)Q(x); gives internally the polynomial:: 1/6+4/6*x^1+4/6*x^2+6/6*x^3+20/6*x^4+16/6*x^5+9/6*x^6+24/6*x^7+16/6*x^8 where all coefficients have the same denominator 6. Notice though that ``\PolToExpr{PQ}`` outputs the ``6/6*x^3`` as ``x^3`` because (by default) it recognizes and filters out coefficients equal to one or minus one (since release ``0.3``). One can use for example ``\PolToCSV{PQ}`` to see the internally stored coefficients. .. [#] prior to ``0.4.1``, ``polexpr`` used to temporarily patch during the parsing of polynomials the xintfrac_ macros. This patch was backported to xint_ at release ``1.3``. - `\\PolDiff{polname_1}{polname_2}`_ always applies ``\xintIrr`` to the resulting coefficients, except that the *power of ten* part ``[N]`` (for example an input in scientific notation such as ``1.23e5`` gives ``123/1[3]`` internally in xintfrac) is not taken into account in the reduction of the fraction. This is tentative and may change. Same remark for `\\PolAntiDiff{polname_1}{polname_2}`_. - Currently, the package stores all coefficients from index ``0`` to index equal to the polynomial degree inside a single macro, as a list. This data structure is obviously very inefficient for polynomials of high degree and few coefficients (as an example with ``\poldef f(x):=x^1000 + x^500;`` the subsequent definition ``\poldef g(x):= f(x)^2;`` will do of the order of 1,000,000 multiplications and additions involvings only zeroes... which does take time). This may change in the future. - As is to be expected internal structures of the package are barely documented and unstable. Don't use them. CHANGE LOG ---------- - v0.1 (2018/01/11): initial release. Features: * The `\\poldef `_ parser itself, * Differentiation and anti-differentiation, * Euclidean division and GCDs, * Various utilities such as `\\PolFromCSV `_, `\\PolMapCoeffs `_, `\\PolToCSV `_, `\\PolToExpr `_, ... Only one-variable polynomials so far. - v0.2 (2018/01/14) * Fix: ``"README thinks \numexpr recognizes ^ operator"``. * Convert README to reStructuredText markup. * Move main documentation from README to separate ``polexpr.txt`` file. * Provide ``polexpr.html`` as obtained via DocUtils_ ``rst2html.py``. * Convert README to (CTAN compatible) Markdown markup. Due to lack of available time the test suite might not be extensive enough. Bug reports are very welcome! - v0.3 (2018/01/17) * bug fixes: - the ``0.1`` `\\PolEval `_ accepted expressions for its second argument, but this was removed by mistake at ``0.2``. Restored. **Attention**: at ``0.4`` this has been reverted again, and `\\PolEval{P}\\AtExpr{foo} `_ syntax is needed for using expressions in the second argument. * incompatible or breaking changes: - `\\PolToExpr `_ now by default uses *descending* powers (it also treats differently coefficients equal to 1 or -1.) Use `\\PolToExpr* `_ for *ascending* powers. - `\\PolEval `_ reduced the output to smallest terms, but as this is costly with big fractions and not needed if e.g. wrapped in an ``\xintRound`` or ``\xintFloat``, this step has been removed; the former meaning is available as `\\PolEvalReduced `_. * new (or newly documented) macros: - `\\PolTypesetCmd `_ - `\\PolTypesetCmdPrefix `_ - `\\PolTypesetMonomialCmd `_ - `\\PolEvalReducedAt `_ - `\\PolToFloatExpr `_ - `\\PolToExprOneTerm `_ - `\\PolToFloatExprOneTerm `_ - `\\PolToExprCmd `_ - `\\PolToFloatExprCmd `_ - `\\PolToExprTermPrefix `_ - `\\PolToExprVar `_ - `\\PolToExprTimes `_ * improvements: - documentation has a table of contents, internal hyperlinks, standardized signature notations and added explanations. - one can do ``\PolLet{g}={f}`` or ``\PolLet{g}{f}``. - ``\PolToExpr{f}`` is highly customizable. - `\\poldef `_ and other defining macros prepare the polynomial functions for usage within ``\xintthefloatexpr`` (or ``\xintdeffloatvar``). Coefficients are pre-rounded to the floating point precision. Indispensible for numerical algorithms, as exact fractions, even reduced, quickly become very big. See the documentation about how to use the exact polynomials also in floating point context. **Attention**: this has been reverted at ``0.4``. The macro `\\PolGenFloatVariant `_ must be used for generation floating point polynomial functions. - v0.3.1 (2018/01/18) Fixes two typos in example code included in the documentation. - v0.4 (2018/02/16) * bug fixes: - when Euclidean division gave a zero remainder, the internal representation of this zero polynomial could be faulty; this could cause mysterious bugs in conjunction with other package macros such as `\\PolMapCoeffs `_. - `\\PolGCD `_ was buggy in case of first polynomial being of lesser degree than the second one. * breaking changes: - formerly `\\PolEval{P}\\At{foo} `_ allowed ``foo`` to be an expression, which was transparently handled via ``\xinttheexpr``. Now, ``foo`` must be a fraction (or a macro expanding to such) in the format acceptable by ``xintfrac.sty`` macros. Use `\\PolEval{P}\\AtExpr{foo} `_ for more general arguments using expression syntax. E.g., if ``foo`` is the name of a variable known to ``\xintexpr``. The same holds for `\\PolEvalReduced `_ and `\\PolFloatEval `_. - the ``3.0`` automatic generation of floating point variants has been reverted. Not only do *not* the package macros automatically generate floating point variants of newly created polynomials, they actually make pre-existing such variant undefined. See `\\PolGenFloatVariant `_. * new non-expandable macros: - `\\PolGenFloatVariant `_ - `\\PolGlobalLet `_ - `\\PolTypesetOne `_ - `\\PolQuo `_ - `\\PolRem `_ - `\\PolToSturm `_ - `\\PolToSturm\* `_ - `\\PolSetToSturmChainSignChangesAt `_ - `\\PolSetToNbOfZerosWithin `_ - `\\PolSturmIsolateZeros `_ - `\\PolRefineInterval* `_ - `\\PolRefineInterval[N] `_ - `\\PolEnsureIntervalLength `_ - `\\PolEnsureIntervalLengths `_ - `\\PolPrintIntervals `_ - `\\PolPrintIntervalsPrintExactZero `_ - `\\PolPrintIntervalsPrintLeftEndPoint `_ - `\\PolPrintIntervalsPrintRightEndPoint `_ - `\\PolReduceCoeffs* `_ - `\\PolMakeMonic `_ * new expandable macros: - `\\PolToExprOneTermStyleA `_ - `\\PolIfCoeffIsPlusOrMinusOne `_ - `\\PolLeadingCoeff `_ - `\\PolSturmChainLength `_ - `\\PolSturmNbOfIsolatedZeros `_ - `\\PolSturmIfZeroExactlyKnown `_ - `\\PolSturmIsolatedZeroLeft `_ - `\\PolSturmIsolatedZeroRight `_ - `\\PolPrintIntervalsTheEndPoint `_ - `\\PolPrintIntervalsTheIndex `_ - `\\PolIfEndPointIsPositive `_ - `\\PolIfEndPointIsNegative `_ - `\\PolIfEndPointIsZero `_ - `\\PolIntervalWidth `_ - `\\PolDecToString `_ * improvements: The main new feature is implementation of the `Sturm algorithm`_ for localization of the real roots of polynomials. - v0.4.1 (2018/03/01) Synced with xint 1.3. - v0.4.2 (2018/03/03) Documentation fix. - v0.5 (2018/04/08) * bug fixes: - `\\PolGet{polname}\\fromarray\\macro`_ crashed when ``\macro`` was an xinttools_ array macro with no items. It now produces the zero polynomial. * breaking changes: - `\\PolToSturm`_ creates primitive integer coefficients polynomials. This speeds up localization of roots via `\\PolSturmIsolateZeros`_. In case of user protests the author will make available again the code producing the bona fide Sturm polynomials as used formerly. - polynomials created from `\\PolFromCSV`_ or `\\PolGet `_ get their coefficients normalized via xintfrac_\ 's ``\xintRaw``. * experimental change: - optional argument to `\\PolSturmIsolateZeros`_ (see `The degree 41 polynomial with -2, -1.9, -1.8, ..., 0, 0.1, ..., 1.9, 2 as roots`_ for usage). It will presumably be replaced in future by an interval specification. * new non-expandable macro: - `\\PolMakePrimitive`_ * new expandable macro: - `\\PolIContent`_ - v0.5.1 (2018/04/22) * new feature: - the character ``'`` can be used in polynomial names. Acknowledgments --------------- Thanks to Jürgen Gilg whose question about xint_ usage for differentiating polynomials was the initial trigger leading to this package, and to Jürgen Gilg and Thomas Söll for testing it on some concrete problems. Renewed thanks on occasion of ``0.4`` release! See README.md for the License. .. _xinttools: .. _xintfrac: .. _xintexpr: .. _xint: http://www.ctan.org/pkg/xint .. _Sturm algorithm: .. _Sturm Theorem: https://en.wikipedia.org/wiki/Sturm%27s_theorem .. _DocUtils: http://docutils.sourceforge.net/docs/index.html