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--[[
This file contains the unit class. It task is keeping
track of the unit terms.
Copyright (c) 2021 Thomas Jenni
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
]]--
local prefix = ... and (...):match '(.-%.?)[^%.]+$' or ''
-- Unit class
local Unit = {}
Unit.__index = Unit
-- make Unit callable
setmetatable(Unit, {
__call = function(class, ...)
return Unit.new(...)
end
})
-- constructor
function Unit.new(...)
local arg = {...}
local u = {}
setmetatable(u, Unit)
-- Unit.new()
if #arg == 0 then
u._term = {{},{}}
u.prefixsymbol = nil
u.prefixname = nil
-- copy constructor
elseif #arg == 1 then
local o = arg[1]
-- check if given object is a unit
if getmetatable(o) ~= Unit then
error("Error: Cannot create a copy of the object, because it's not a unit.")
end
u.prefixsymbol = o.prefixsymbol
u.prefixname = o.prefixname
u._term = o._term
-- Unit.new(symbol, name)
elseif #arg == 2 then
u.symbol = arg[1]
u.name = arg[2]
u._term = {{{u,1}},{}}
-- Unit.new(symbol, name, prefixsymbol, prefixname)
elseif #arg == 4 then
u.symbol = arg[1]
u.name = arg[2]
u.prefixsymbol = arg[3]
u.prefixname = arg[4]
u._term = {{{u,1}},{}}
else
error("Wrong number of arguments. Cannot create the unit.")
end
return u
end
function Unit.__mul(o1,o2)
local u = Unit.new()
u:_append(o1)
u:_append(o2)
return u
end
function Unit.__div(o1,o2)
local u = Unit.new()
u:_append(o1)
u:_append(o2, true)
return u
end
function Unit.__pow(o,n)
local u = Unit.new()
-- invert the term
if n < 0 then
u:_append(o,true)
n = -n
else
u:_append(o)
end
-- multiply term by factor n
for i=1,2 do
local part = u._term[i]
for j=1,#part do
part[j][2] = part[j][2] * n
end
end
return u
end
--copy units from an other quantity
function Unit:_append(u, inversed)
local s = {1,2}
if inversed then
s = {2,1}
end
for i=1,2 do
local part = u._term[s[i]]
local term = self._term[i]
for j=1,#part do
local unit = part[j][1]
local exponent = part[j][2]
term[#term + 1] = {unit, exponent}
end
end
end
-- convert quantity to a string
function Unit:__tostring()
-- assemble unit strings
local u = {{},{}}
for i=1,2 do
local units = self._term[i]
for j=1,#units do
local unit = units[j]
local exponent = unit[2]
if exponent ~= 0 then
local symbol = unit[1].symbol
local s = "_"
if unit[1].prefixsymbol ~= nil then
s = s..unit[1].prefixsymbol
end
if symbol ~= nil then
s = s..symbol
end
if exponent ~= 1 then
s = s.."^"..exponent
end
table.insert(u[i], s)
end
end
end
local str = ""
-- write enumerator
if #u[1] > 0 then
str = str.." * "..table.concat(u[1], " * ")
end
-- write division sign
if #u[2] > 0 then
str = str.." / "
end
-- write denominator
if #u[2] > 1 then
str = str.."("..table.concat(u[2], " * ")..")"
else
str = str..table.concat(u[2], " * ")
end
return str
end
-- convert the unit to a unit string which can be read from the latex package siunitx.
function Unit:tosiunitx()
local s = ""
for i=1,2 do
local units = self._term[i]
for j=1,#units do
local unit = units[j]
local e = unit[2]
if e ~= 0 then
if i == 2 then
s = s.."\\per"
end
if unit[1].prefixname ~= nil then
s = s.."\\"..unit[1].prefixname
end
s = s.."\\"..unit[1].name
if e ~= 1 then
s = s.."\\tothe{"..e.."}"
end
end
end
end
return s
end
return Unit
|
