--[[ 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