Return (a + b, "17 + 25") instead of (a + b, "a + b") for #stringify(a + b)

[narayana]

let a = 17
let b = 25
I would like to get (a + b, "17 + 25") instead of (a + b, "a + b") for #stringify(a + b)

I would like to read a, b values dynamically in the macro plugin. Please suggest how to read a, b values dynamically.

Thanks in advance.

[ahoppen (Alex Hoppen)]

Hello @narayana,

That’s not possible. Remember that macros are a syntactic transformation at compile-time, not runtime. And at compiler time, we can’t know the values of a and b in general, for example consider if you had

let a = loadValueFromTheInternet()

What would a be in that case at compile time? The answer is: We don’t know because loadValueFromTheInternet() will only be executed when your program is run, not during compilation.

[Joe_Groff]

Maybe a slightly different macro and library design could get the desired effect. How about a macro that performs a transformation that turns x + y into a closure using string interpolations, like { "\(x) + \(y)" }? There would however need to be some purely syntactic rule in the macro to decide what to interpolate, maybe only bare identifier declaration references or something like that.

[narayana]

Thanks Alex and Joe for the valuable information.