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+%% This is part of OpTeX project, see http://petr.olsak.net/optex
+
+\_codedecl \newif {Special if-macros, is-macros and loops <2020-05-02>} % preloaded in format
+
+ \_doc ----------------------------
+ \secc Classical \code{\\newif}
+ The \`\newif` macro implements boolean value.
+ It works as in plain \TeX. It means that
+ after `\newif\ifxxx` you can use `\xxxtrue` or
+ `\xxxfalse` to set the boolean value and use `\ifxxx true\else false\fi`
+ to test this value. The default value is false.
+
+ The macro \`\_newifi` enables to declare `\_ifxxx` and to use `\_xxxtrue` and
+ `\_xxxfalse`. This means that it is usable for internal name space
+ (`_`prefixed macros).
+ \_cod ----------------------------
+
+\_def\_newif #1{\_ea\_newifA \_string #1\_relax#1}
+\_ea\_def \_ea\_newifA \_string\if #1\_relax#2{%
+ \_sdef{#1true}{\_let#2=\_iftrue}%
+ \_sdef{#1false}{\_let#2=\_iffalse}%
+ \_let#2=\_iffalse
+}
+\_def\_newifi #1{\_ea\_newifiA \string#1\_relax#1}
+\_ea\_def \_ea\_newifiA \_string\_if #1\_relax#2{%
+ \_sdef{_#1true}{\_let#2=\_iftrue}%
+ \_sdef{_#1false}{\_let#2=\_iffalse}%
+ \_let#2=\_iffalse
+}
+\_public \newif ;
+
+ \_doc ----------------------------
+ \secc Loops
+ The \`\loop` `<codeA> \ifsomething <codeB>` \`\repeat` loops `<codeA><codeB>`
+ until `\ifsomething` is false. Then `<codeB>` is not executed and loop is
+ finished. This works like in plain \TeX, but implementation is somewhat
+ better (you can use `\else` clause after the `\ifsomething`).
+
+ There are public version `\loop...\repeat` and private version
+ \`\_loop` ...\`\_repeat`. You cannot mix both versions in one loop.
+
+ The `\loop` macro keeps its original plain TeX meaning. It is not
+ expandable and nested `\loop`s are possible only in a \TeX/ group.
+ \_cod ----------------------------
+
+\_long\_def \_loop #1\_repeat{\_def\_body{#1}\_iterate}
+\_def \loop #1\repeat{\_def\_body{#1}\_iterate}
+\_let \_repeat=\_fi % this makes \loop...\if...\repeat skippable
+\_let \repeat=\_fi
+\_def \_iterate {\_body \_ea \_iterate \_fi}
+
+ \_doc -----------------------------
+ \`\foreach` `<list>` \`\do` `{<what>}`
+ repeats `<what>` for each element of the
+ `<list>`. The `<what>` can include `#1` which is substituted by each
+ element of the `<list>`. The macro is expandable.
+
+ \`\fornum` `<from>..<to>` \`\do` `{<what>}` or
+ \`\fornumstep` `<num>: <from>..<to>` \`\do` `{<what>}`
+ repeats `<what>` for each number from `<from>` to `<to>` (with step `<num>`
+ or with step one). The `<what>` can include `#1` which is substituted by
+ current number. The sequence `<from>..<to>` can be decreasing too.
+ The macro is expandable.
+
+ Recommendation: it is better to
+ use private variants of \`\_foreach` and \`\_fornum`.
+ When the user writes `\input tikz` then `\foreach` macro is redefined! The
+ private variants use \`\_do` separator instead `\do` separator.
+ \_cod -----------------------------
+
+\_newcount\_frnum % the numeric variable used in \fornum
+\_def\_do{\_doundefined} % we need to ask \_ifx#1\_do ...
+
+\_long\_def\_foreach #1\_do#2{\_putforstack
+ \_immediateassignment\_def\_fbody##1{#2}%
+ \_foreachA #1\_do}
+\_long\_def\_foreachA #1{\_ifx\_do#1\_getforstack\_else\_fbody{#1}\_ea\_foreachA\_fi}
+
+\_def\_fornum#1..#2\_do{\_fornumstep 1:#1..#2\_do}
+\_long\_def\_fornumstep#1:#2..#3\_do#4{\_putforstack
+ \_immediateassigned{%
+ \_def\_fbody##1{#4}%
+ \_def\_fornumsgn{}%
+ \_def\_fornumrel{<}%
+ \_frnum=\_numexpr#2\_relax
+ \_ifnum\_numexpr#3<\_frnum \_def\_fornumrel{>}\_fi %decreasing sequence
+ \_ifnum\_numexpr#1\_fornumrel0 \_def\_fornumsgn{-}\_fi % correction
+ }%
+ \_fornumB{#3}{#1}%
+}
+\_def\_fornumB #1#2{\_ifnum\_numexpr#1\_fornumrel\_frnum \_getforstack \_else
+ \_ea\_fbody\_ea{\_the\_frnum}%
+ \_immediateassignment\_advance\_frnum by\_numexpr\_fornumsgn#2\_relax
+ \_afterfi{\_fornumB{#1}{#2}}\_fi
+}
+\_def\_afterfi#1#2\_fi{\_fi#1}
+
+\_def\foreach #1\do{\_foreach #1\_do}
+\_def\fornum#1..#2\do{\_fornumstep 1:#1..#2\_do}
+\_def\fornumstep#1:#2..#3\do{\_fornumstep #1:#2..#3\_do}
+
+ \_doc ----------------------------
+ The `\foreach` and `\fornum` macros can be nested and arbitrary combined.
+ When they are nested then use `##1` for the variable of nested level,
+ `####1` for the variable of second nested level etc. Example:
+ \begtt
+ \foreach ABC \do {\fornum 1..5 \do {letter:#1, number: ##1. }}
+ \endtt
+ Implementation note:
+ we cannot use \TeX/-groups for nesting levels because we want to do the
+ macros expandable. We must implement a special for-stack which saves the
+ data needed by `\foreach` and `\fornum`. The \`\_putforstack` is used
+ when `\for*` is initialized and \`\_getforstack` is used when the
+ `\for*` macro ends. The \`\_forlevel` variable keeps the current nesting
+ level. If it is zero, then we need not save nor restore any data.
+ \_cod ----------------------------
+
+\_newcount\_forlevel
+\_def\_putforstack{\_immediateassigned{%
+ \_ifnum\_forlevel>0
+ \_sdef{_frnum:\_the\_forlevel\_ea}\_ea{\_the\_frnum}%
+ \_slet{_fbody:\_the\_forlevel}{_fbody}%
+ \_fi
+ \_advance\_forlevel by1
+}}
+\_def\_getforstack{\_immediateassigned{%
+ \_advance\_forlevel by-1
+ \_ifnum\_forlevel>0
+ \_slet{_fbody}{_fbody:\_the\_forlevel}%
+ \_frnum=\_cs{_frnum:\_the\_forlevel}\_space
+ \_fi
+}}
+
+ \_doc ----------------------------
+ \secc Is-macros
+ There are a collection of macros
+ `\isempty`, `\istoksempty`, `\isequal`, `\ismacro`, `\isdefined`, `\isinlist` and `\isfile`
+ with common syntax:
+ \begtt \catcode`\<=13
+ \issomething <params> \iftrue <codeA> \else <codeB> \fi
+ or
+ \issomething <params> \iffalse <codeB> \else <codeA> \fi
+ \endtt
+ The `\else` part is optional. The `<codeA>` is processed if
+ `\issomething<params>` generates true condition. The `<codeB>`
+ is processed if `\issomething<params>` generates false condition.
+
+ The `\iftrue` or `\iffalse` is an integral part of this syntax
+ because we need to keep skippable nested `\if` conditions.
+
+ Implementation note:
+ we read this `\iftrue` or `\iffalse` into unseparated parameter and repeat
+ it because we need to remove an optional space before this command.
+
+ \medskip\noindent
+ \`\isempty` `{<text>}\iftrue`
+ is true if the `<text>` is empty. This macro is expandable.\nl
+ \`\istoksempty` `<tokens variable>\iftrue`
+ is true if the `<tokens variable>` is empty. It is expandable.
+ \_cod ----------------------------
+
+\_def \_isempty #1#2{\_if\_relax\_detokenize{#1}\_relax \_else \_ea\_unless \_fi#2}
+\_def \_istoksempty #1#2{\_ea\_isempty\_ea{\_the#1}#2}
+\_public \isempty \istoksempty ;
+
+ \_doc ----------------------------
+ \`\isequal` `{<textA>}{<textB>}\iftrue`
+ is true if the <textA> and <textB> are
+ equal, only from strings point of view, category codes are ignored.
+ The macro is expandable.
+ \_cod ----------------------------
+
+\_def\_isequal#1#2#3{\_directlua{%
+ if "\_luaescapestring{\_detokenize{#1}}"=="\_luaescapestring{\_detokenize{#2}}"
+ then else tex.print("\_nbb unless") end}#3}
+\_public \isequal ;
+
+ \_doc ----------------------------
+ \`\ismacro` `\macro{text}\iftrue` is true if macro is defined as {<text>}.
+ Category codes are ignored in this testing. The macro is expandable.
+ \_cod ----------------------------
+
+\_def\_ismacro#1{\_ea\_isequal\_ea{#1}}
+\_public \ismacro ;
+
+ \_doc ----------------------------
+ \`\isdefined` `{<csname>}\iftrue` is true if `\<csname>` is defined.
+ The macro is expandable.
+ \_cod ----------------------------
+
+\_def\_isdefined #1#2{\_ifcsname #1\_endcsname \_else \_ea\_unless \_fi #2}
+\_public \isdefined ;
+
+ \_doc ----------------------------
+ \`\isinlist` `\list{<text>}\iftrue` is true if the
+ `<text>` is included the macro body of the `\list`.
+ The category code are relevant here. The macro is not expandable.
+ \_cod ----------------------------
+
+\_long\_def\_isinlist#1#2{\_begingroup
+ \_long\_def\_tmp##1#2##2\_end/_%
+ {\_endgroup\_if\_relax\_detokenize{##2}\_relax \_ea\_unless\_fi}%
+ \_ea\_tmp#1\_endlistsep#2\_end/_%
+}
+\_public \isinlist ;
+
+ \_doc -----------------------------
+ \`\isfile` `{<filename>}\iftrue` is true if the file <filename> exists and are
+ readable by \TeX.
+ \_cod -----------------------------
+
+\_newread \_testin
+\_def\_isfile #1{%
+ \_openin\_testin ={#1}\_relax
+ \_ifeof\_testin \_ea\_unless
+ \_else \_closein\_testin
+ \_fi
+}
+\_public \isfile ;
+
+ \_doc -----------------------------
+ \`\isfont` `{<fontname or [fontfile]>}\iftrue`
+ is true if given font exists. The result of this testing
+ is saved to the \`\_ifexistfam`.
+ \_cod -----------------------------
+
+\_newifi \_ifexistfam
+\_def\_isfont#1#2{%
+ \_begingroup
+ \_suppressfontnotfounderror=1
+ \_font\_testfont={#1}\_relax
+ \_ifx\_testfont\_nullfont \_def\_tmp{\_existfamfalse \_unless}
+ \_else \_def\_tmp{\_existfamtrue}\_fi
+ \_ea \_endgroup \_tmp #2%
+}
+\_public \isfont ;
+
+ \_doc ----------------------------
+ The last macro \`\isnextchar` `<char>{<codeA>}{<codeB>}`
+ has different syntax than all others is-macros.
+ It executes `<codeA>` if next character is equal to <char>.
+ Else the `<codeB>` is executed. The macro is not expandable.
+ \_cod ----------------------------
+
+\_long\_def\_isnextchar#1#2#3{\_begingroup\_toks0={\_endgroup#2}\_toks1={\_endgroup#3}%
+ \_let\_tmp=#1\_futurelet\_next\_isnextcharA
+}
+\_def\_isnextcharA{\_the\_toks\_ifx\_tmp\_next0\_else1\_fi\_space}
+
+\_public \isnextchar ;
+
+
+\_endcode
+
+2020-05-02 \newif bug fix
+2020-04-15 \fornumstep 3: 1..12 instead \fornum 1..12\step 3
+2020-04-15 \fornum, \foreach can be nested without groups
+2020-04-01 implemented