Re: Special Code String for mixins

[Jonathan Marler via Digitalmars-d]

On Wednesday, 15 March 2017 at 13:50:28 UTC, Inquie wrote:
I hate building code strings for string mixins as it's very 
ugly and seems like a complete hack.

How bout, instead, we have a special code string similar to a 
multiline string that allows us to represent valid D code. The 
compiler can then verify the string after compilation to make 
sure it is valid D code(since it ultimately is a compile time 
constant).

e.g.,

string s = "smile";
enum code1 = @#
void happyCode = "Makes me @@s@@";
#@

enum code2 = code1 ~ @#
int ImThisHappy = @@s.length@@;
#@

mixin(code);

or

mixin(code.stringof); // possible to convert code string to a 
string and vice versa.


or whatever syntax one thinks is better. The point is that the 
code string is specified different and then is no longer 
ambiguous as a normal string. Compilers and IDE's can make more 
informed decisions.

There might be a much better way, but something should be done 
to clean up this area of D. It is a mess to have to use string 
building to create code. (it's amazingly powerful, but still a 
mess)

I've got a PR for dmd (https://github.com/dlang/dmd/pull/7988) 
that implements "interpolated strings" which makes generating 
code with strings MUCH nicer, i.e.

string generateFunction(string attributes, string returnType, 
string name, string args, string body)
{
    import std.conv : text;
    return text(iq{
    // This is an interpolated string!
    $(attributes) $(returnType) $(name)($(args))
    {
        $(body)
    }
    });
}

// Let's use it:
mixin(generateFunction("pragma(inline)", "int", "add", "int a, 
int b", "return a + b;"));

assert(100 == add(25, 75));