Implement string formatting syntax in RGBASM

[PikalaxALT]

Implement a function, STRFMT(spec, ...) which takes string spec and formats following arguments into the fields specified in spec, similar to std::printf. Minimally, support %s, %d, %f, %x.

VAL1 = STRFMT("Hello %s! I am %d years old today!", "world", $f)
PRINTT "{VAL1}\n"

should yield

Hello world! I am 15 years old today!

[ekimekim]

This would be the ideal general solution, though right now i'd settle for just some way to format a value as decimal rather than hex.

[ISSOtm]

Fact: we will not be passing the string directly to printf because of not trusting user input (say hi to %n) and trying to parse the string for sanitization amounts to, well, parsing it ourselves.

Considering this, what features would be desired? (Zero-padding, minimum lengths, argument reordering perhaps?)

[AntonioND]

I would keep it simple. No argument reordering. Probably minimum leading zeroes/spaces.

[Rangi42]

Leading zeros/spaces, and d/x/X/b/o to support the same integer bases for which there are literals.

Also maybe trailing spaces with -. So STRFMT("%-4d", N) where N == 42 gives "42__". Or STRFMT("%-10s", Hi) where Hi is "hello" gives "hello_____".