Ptr
Ptr is a parse tree: a graph-like hierarchical representation of a program designed to preserve all information that programmers entered. This means including layout, comments, indentation, annotations, etc. In Rascal Ptr and Cst are interchangeable because there is evidence that this makes language engineers more efficient. However, in order to demonstrate Ptr in our case study, we used purely lexical definitions (so called "character level grammars"), which are otherwise uncommon in Rascal. Layout is explicitly defined empty, because otherwise Rascal parser generator will fall back to default layout definition.
NB: renderParsetree from vis::ParseTree does not show anything here, because it was written to ignore lexical structure.
module types::Ptr
import ParseTree;
import vis::ParseTree;
import IO;
layout L = ();
lexical WS = [\ \t\n\r];
lexical Ptr = PtrLHS lhs WS* "=" WS* PtrRHS rhs WS* ";";
lexical PtrLHS = PtrName f WS* PtrNameArgs args;
lexical PtrRHS = PtrExpr rhs;
lexical PtrNameArgs = {PtrName WS*}+ ns;
lexical PtrExpr
= PtrAtom a
> left PtrExpr l WS* "*" WS* PtrExpr r
> left PtrExpr l WS* "+" WS* PtrExpr r
;
lexical PtrAtom
= PtrName name
| PtrNumber number
;
lexical PtrName = [a-z]+ !>> [a-z];
lexical PtrNumber = [0-9]+ !>> [0-9];
public bool validate(Ptr p) = /amb(_) !:= p;
public void visualise(Ptr p) = renderParsetree(p);
Ptr example = parse(#Ptr,"f arg = arg +1;");
Ptr defexample = parse(#Ptr,"f arg = arg + 1 ;");
Ptr tricky = parse(#Ptr,"f arg = 1+2*2+1;");
Ptr multi = parse(#Ptr,"add x y = x+y ;");
test bool vptr1() = validate(example);
test bool vptr2() = validate(defexample);
test bool vptr3() = validate(tricky);
void visptr1() = visualise(example);
void visptr2() = visualise(tricky);