i wanted to rewrite this code
local tb = {}
local meta = {}
function tb.new(b)
local super = {}
super.b = b
setmetatable(super,meta)
return super
end
function tb.add(s1,s2)
return s1.b+s2.b
end
meta.__concat = tb.add
f= tb.new(3)
t= tb.new(4)
print(f..t)
in tb = setmetable({},(metamethod) style and i came up with this
local tb = setmetatable({},{__concat = function(a,b)
return a+b
end
})
function ins(a)
tb.a = a
return tb.a
end
print(ins(2)..ins(3))
i want to know why its not working , i admit i got no idea what im doing and how many words does this post need ;-;
print(ins(2)..ins(3))
resolves to
print( 2 .. 3)
which resolves to
print("2" .. "3")
which resolves to
print("23")
which outputs 23
Both numbers are implicitly converted to their string representation, then they are concatenated to a single string "23"
From the Lua 5.4 Reference Manual: 3.4.6 Concatenation:
The string concatenation operator in Lua is denoted by two dots ('..'). If both operands are strings or numbers, then the numbers are converted to strings in a non-specified format (see §3.4.3). Otherwise, the __concat metamethod is called (see §2.4).
Your first snippet concatenates two tables while your second snippet concatenates two numbers. So in the second case the __concat metamethod is never invoked.
Just use print(ins(2) + ins(3)) if you want to add those two numbers. I don't see why you should replace simple arithmetic operators. That just adds unnecessary confusion.
You would have to concatenate tb with something to invoke your __concat, not its fields.