Fix + operator overloading

README.md

@@ -194,7 +194,7 @@ $ f(a, b...)
 ~ f("discarded")
 ```
 
-Functions with the same name can be defined, as long as they have a different number of argument.
+Functions with the same name can be defined, as long as they have a different number of argument. Functions will be selected based on the number of arguments given:
 
 ```
 $ f(a, b)

anselme.lua

@@ -7,11 +7,11 @@ local anselme = {
 }
 package.loaded[...] = anselme
 
--- TODO: for type checking functions:
+-- TODO: improve type checking.
--- pour éliminer totalement les undefined
+-- Right now, there is some basic type checking done at parsing - but since Lua and Anselme functions may not always define the type of
--- ne type checker/compiler les fonctions que lorsqu'elles sont apppelées, en déterminant leur type à ce moment là selon les arguments donnés
+-- their parameters and return value, a lot of checks are skipped ("undefined argument" type).
--- (du coup la surcharge ne se fera que selon l'arité. Mais ça sera 100% type checké)
+-- Probably won't be able to remove them completely (since lists can have mixed types, etc.), but would be good to limit them.
--- PB: les listes ont des types mixés (cf les varargs) + afficher des warnings dans le selecteur de variante lorsqu'un type de retour manque
+-- Ideally, we'd avoid runtime type checking.
 
 -- load libs
 local preparse = require((...):gsub("anselme$", "parser.preparser"))

stdlib/functions.lua

@@ -133,12 +133,14 @@ functions = {
 	-- arithmetic
 	["+"] = {
 		{
-			arity = 2, types = { "number", "number" }, return_type = "number",
+			arity = 2,
-			value = function(a, b) return a + b end
+			value = function(a, b)
-		},
+				if type(a) == "string" then
-		{
+					return a .. b
-			arity = 2, types = { "string", "string" }, return_type = "string",
+				else
-			value = function(a, b) return a .. b end
+					return a + b
+				end
+			end
 		}
 	},
 	["-"] = {