Parse

rascal-0.40.17

Synopsis

Parse a Func program from a string or a file.

Description

Parsing uses the syntax rules for a given start non-terminnal to parse a string and turn it into a parse tree. The work horse is the parse function that is available in the ParseTree library.

Examples

Here is how to parse Func programs from a string or file:

module demo::lang::Func::Parse

import demo::lang::Func::Func;
import ParseTree;

Prog parse(loc l) = parse(#Prog, l);
Prog parse(str s) = parse(#Prog, s);

Let's try this on example F0.func:

fact(n) = if n <= 1 then
             1 
          else 
             n * fact(n-1)
          end

First, we try the version with a string argument:

rascal>import demo::lang::Func::Parse;
ok
rascal>import demo::lang::Func::programs::F0;
ok
rascal>parse(F0);
Prog: (Prog) `fact(n) = if n <= 1 then
             1 
          else 
             n * fact(n-1)
          end`

This must be defined as success: we get the original program and its parse tree back. Next, we try the same from a file. We use the scheme std that refers to files that reside in the Rascal library. See Location for further details on other schemes.

rascal>parse(|project://rascal-website/courses/Recipes/demo/lang/Func/programs/F0.func|);
Prog: (Prog) `fact(n) = if n <= 1 then
             1 
          else 
             n * fact(n-1)
          end`