I would like to know how I can handle multiple optionals without concrete pattern matching for each possible permutation.
Below is a simplified example of the problem I am facing:
lexical Int = [0-9]+;
syntax Bool = "True" | "False";
syntax Period = "Day" | "Month" | "Quarter" | "Year";
layout Standard = [\ \t\n\f\r]*;
syntax Optionals = Int? i Bool? b Period? p;
str printOptionals(Optionals opt){
str res = "";
if(!isEmpty("<opt.i>")) { // opt has i is always true (same for opt.i?)
res += printInt(opt.i);
}
if(!isEmpty("<opt.b>")){
res += printBool(opt.b);
}
if(!isEmpty("<opt.p>")) {
res += printPeriod(opt.period);
}
return res;
}
str printInt(Int i) = "<i>";
str printBool(Bool b) = "<b>";
str printPeriod(Period p) = "<p>";
However this gives the error message:
The called signature: printInt(opt(lex("Int"))), does not match the declared signature: str printInt(sort("Int"));
How do I get rid of the opt part when I know it is there?
I'm not sure how ideal this is, but you could do this for now:
if (/Int i := opt.i) {
res += printInt(i);
}
This will extract the Int
from within opt.i
if it is there, but the match will fail if Int
was not provided as one of the options.