Support string concatenation.

[Moderocky]

Summary

1. Allows the joining of strings with +, e.g. "foo" + "bar" = "foobar".
   Does not allow the joining of strings and numbers or other non-coercible objects.
2. Adds a var-args concat(...) function that permits joining anything into a single string (including non-texts).

Description

I'm not a fan of strings as they are in Skript: I dislike that there's no true literal, I dislike how cumbersome and inefficient "%...%" interpolation is (both to write and to actually evaluate).
Aside from interpolation, our only other option for joining strings is the expression (concat[enate]|join) %texts% [(with|using|by) [[the] delimiter] %text%] which has a rather unpleasant pattern (it sounds more like an effect than an expression).
This is designed for joining texts, but it can't coerce types properly, so you still end up needing to use interpolation (or store things in middle man variables) to actually join things that aren't strings (e.g. "your lucky number is " and 66).

What This Doesn't Do

In 2.7 or 2.8 (I forget which) a deliberate change was made to make illegal expressions in maths completely fail (evaluate to <none>) rather than be permitted as 0.
This doesn't change that. This doesn't permit you to add "hello" and 81: it will fail at parsing time and, even if you try and get around that with variables, it will still evaluate to <none> as intended.

String addition ONLY supports adding strings together, whether they're from expressions, variables or "...".

broadcast "hello" + "world" # OK!

set {var} to "..."
broadcast "hello" + {var} # OK

broadcast "hello" + [some string expression] # OK

broadcast "hello" + 1 # NOT OK! Fails at parse time

set {var} to 1
broadcast "hello" + {var} # NOT OK! Bad math to <none>

broadcast "hello" + [some non-string expression] # NOT OK! Probably fails at parse time

String Addition

This pull request adds string addition arithmetic: "A" + "B" = "AB".

Lots of languages allow you to concatenate (glue together) strings. Most languages use +, some like to do their own thing with . or & or some other joiner.
Just because other languages do something isn't a sufficient reason to add it to Skript, though.

I like it as a feature:

• I think it's arguably cleaner and neater than "%...%" (especially if you have multiple interpolations in one text!)
• It's especially cleaner than trying to use an expression (and heaven forbid a text) inside an interpolation, where you're having to double your quotes and whatever.
• I think, realistically, it's more immediately understandable to a beginner that "a" + "b" = "ab" than whatever's going on with "a%""b""%".
• It ought to be safer/easier for the machine to interpret, interpolation's usually pretty heavy (although this is Skript, who knows).

String concat(...) Function

This pull request adds a concat(...) variable arguments function.
This is more advanced than the concatenate|join expression, since it properly supports non-text parameters even without coercion.

Concat takes in multiple objects and returns the result of all of them stringified and glued together.

concat("hello") = "hello"
concat("hello", " world") # "hello world"
concat("hello", " ", "there") # "hello there"

set {_var} to "hello"
concat({_var}, " world") # "hello world"

Concat allows the joining of strings and objects, which are run through Classes.toString.

concat("foo", 1) # "foo1"
concat("my nice new ", stone sword) # "my nice new stone sword"

Concat ALWAYS returns a text, even if none of the inputs are text. It doesn't do maths evaluation, it purely joins things into a text.

concat(1, 2) # "12"
concat(1, 2, 3) # "123"
concat(stone sword, stone sword) # "stone swordstone sword"

---

Target Minecraft Versions: any
Requirements: none
Related Issues: none

[AyhamAl-Ali]

Wonderful 🎉 Let's hope it doesn't break anything we didn't think of

[UnderscoreTud]

For string + string should we treat an empty variable as an empty string? E.x. "some string" + {_none} = "some string"

[Moderocky]

For string + string should we treat an empty variable as an empty string? E.x. "some string" + {_none} = "some string"

Do you have a suggestion? I feel like it shouldn't return nothing as the result like with invalid math.

[UnderscoreTud]

For string + string should we treat an empty variable as an empty string? E.x. "some string" + {_none} = "some string"

Do you have a suggestion? I feel like it shouldn't return nothing as the result like with invalid math.

You can do that by registering a default value for strings using Arithmetics.registerDefaultValue

[Moderocky]

You can do that by registering a default value for strings using Arithmetics.registerDefaultValue

Yes I know, I was asking what you think the default should be (if not what it is now).

[UnderscoreTud]

You can do that by registering a default value for strings using Arithmetics.registerDefaultValue

Yes I know, I was asking what you think the default should be (if not what it is now).

You can just make it an empty string