What is the fsyacc equivalent for the following ocamlyacc code?

3
votes

I'm working on a toy compiler using F#, i.e., the combo of FsLex and FsYacc. To get familiar with them, I've read the Lexer/Parser chapter of Expert F# (v2) book (a good book btw). Right now, I've half way through the well-recommended ocamlyacc tutorial, and stuck at the last example Multi-Function Calculator mfcalc. Particularly, the following statement

%token <float->float> FNCT

in the parser file keeps getting error "error: parse error" in my F# version. Am I missing anything here, or is this a feature currently not supported by F#?

2
f#fsyacc

2 Answers

4
votes

This looks like a bug. Adding parens doesn't help. I have tried various workarounds, but I couldn't find a clean way. You should do a bug report.

If you have only one function (like in the tutorial example), you should define a type in the prelude:

type floatFunction = float -> float
...
%token <floatFunction> FNCT

If you have many functions, you could also define a generic type:

type functionType<'a, 'b> = 'a -> 'b
...
%token < ('a, 'b) functionType > FNCT

Any angle bracket in the type leads to a parse error (even functionType<float,float>).

0
votes

You might need to put parens, like

%token <(float->float)> FNCT

I forget (am away from an F# machine to check).