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diff --git a/Master/texmf-dist/scripts/lua-physical/physical-dimension.lua b/Master/texmf-dist/scripts/lua-physical/physical-dimension.lua
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+--[[
+The Dimension class keeps track of the dimenionality of a physical quantity.
+It can be used to perform validity checks on mathematical operations such as
+addition and subtraction.
+
+Copyright (c) 2020 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 Dimension = {}
+Dimension.__index = Dimension
+
+-- make the table callable
+setmetatable(Dimension, {
+ __call = function(class, ...)
+ return Dimension.new(...)
+ end
+})
+
+-- index for the dimension names
+Dimension._index = {}
+
+-- registry for base dimensions
+Dimension._base = {}
+
+
+-- constructor
+function Dimension.new(d)
+
+ -- string
+ if type(d) == "string" then
+ return Dimension._index[d]
+ end
+
+ local e = {}
+ setmetatable(e, Dimension)
+
+ -- copy constructor
+ if getmetatable(d) == Dimension then
+ for i=1, #Dimension._base do
+ e[i] = d[i] or 0
+ end
+
+ -- create zero dimension
+ else
+ for i=1, #Dimension._base do
+ e[i] = 0
+ end
+ end
+
+ return e
+end
+
+
+-- define a base new dimension
+function Dimension.defineBase(symbol, name)
+
+ local index = Dimension._index
+
+ if index[name] ~= nil then
+ error("Error: Base dimension '"..name.."' does already exist.")
+
+ elseif index[symbol] ~= nil then
+ error("Error: Base dimension '"..symbol.."' does already exist.")
+
+ end
+
+ -- create new dimension
+ local base = Dimension._base
+
+ local n = #base + 1
+ local d = Dimension.new()
+ d[n] = 1
+ d.symbol = symbol
+
+ -- add to registry
+ base[n] = d
+
+ -- resize all other base dimension vectors
+ for i=1, n-1 do
+ base[i][n] = 0
+ end
+
+ -- update index
+ index[symbol] = d
+ index[name] = d
+
+ return d
+end
+
+
+-- define a new derived dimension
+function Dimension.define(name, o)
+
+ local index = Dimension._index
+
+ if index[name] ~= nil then
+ error("Error. Dimension '"..name.."' is already defined.")
+
+ elseif getmetatable(o) ~= Dimension then
+ error("Error. Object in definition of '"..name.."' is no dimension.")
+
+ end
+
+ index[name] = o
+
+ return o
+end
+
+
+-- check if the dimension vector has length zero
+function Dimension.iszero(o)
+ for i=1,#Dimension._base do
+ if o[i] ~= 0 then
+ return false
+ end
+ end
+
+ return true
+end
+
+
+-- test if two dimensions are equal
+function Dimension.__eq(d1, d2)
+ for i=1, #Dimension._base do
+ if d1[i] ~= d2[i] then
+ return false
+ end
+ end
+
+ return true
+end
+
+
+-- add two dimensions
+function Dimension.__add(d1,d2)
+ error("Error: Cannot add dimension objects.")
+end
+
+
+-- subtract two dimensions
+function Dimension.__sub(d1,d2)
+ error("Error: Cannot subtract dimension objects.")
+end
+
+
+-- multiply two dimensions
+function Dimension.__mul(d1,d2)
+ local d = Dimension.new(d1)
+
+ for i=1, #Dimension._base do
+ d[i] = d1[i] + d2[i]
+ end
+
+ return d
+end
+
+
+-- divide two dimensions
+function Dimension.__div(d1,d2)
+ local d = Dimension.new(d1)
+
+ if type(d1) == "number" then
+ for i=1, #Dimension._base do
+ d[i] = 0 - d2[i]
+ end
+ else
+ for i=1, #Dimension._base do
+ d[i] = d1[i] - d2[i]
+ end
+ end
+
+ return d
+end
+
+
+-- raise a dimension to the power
+function Dimension:__pow(n)
+ if type(n) ~= "number" then
+ error("Error: The exponent of the power operation has to be a number.")
+ end
+
+ local d = Dimension.new()
+
+ for i=1, #Dimension._base do
+ d[i] = self[i] * n
+ end
+
+ return d
+end
+
+
+-- convert dimension to a string
+function Dimension:__tostring()
+
+ local result = {}
+
+ -- search for the name of the dimension
+ for name,d in pairs(Dimension._index) do
+ if d == self then
+ result[#result + 1] = name
+ end
+ end
+
+ if #result ~= 0 then
+ return "["..table.concat(result,",").."]"
+ end
+
+ -- assemble dimension from base dimensions
+ local base = Dimension._base
+ for i=1,#base do
+ if self[i] ~= 0 then
+ local dim = "["..base[i].symbol.."]"
+
+ if self[i] ~= 1 then
+ dim = dim.."^"..self[i]
+ end
+
+ result[#result + 1]= dim
+ end
+ end
+
+ return table.concat(result," ")
+
+end
+
+return Dimension \ No newline at end of file