reimplement the subgrammar mutation in Rascal

shared/rascal/src/export/BNF.rsc

@@ -11,8 +11,9 @@ public str pp(BGFProdList ps) = mapjoin(pp,ps,"\n");
 
 public str pp(set[BGFProduction] ps) = mapjoin(pp,ps,"\n");
 
-public str pp(production("",str lhs, BGFExpression rhs)) = "<lhs> ::= <pptop(rhs)> ;";
-public default str pp(BGFProduction p) = "[<p.label>] <p.lhs> ::= <pptop(p.rhs)> ;";
+public str pp(BGFProduction p) = "<ppl(p.label)><p.lhs> ::= <pptop(p.rhs)> ;";
+
+str ppl(str s) = (s=="")?"":"[<s>] ";
 
 str pptop(sequence(BGFExprList es)) = pp(es);
 default str pptop(BGFExpression e) = pp(e);

shared/rascal/src/export/XBNF.rsc

@@ -78,3 +78,5 @@ str pp(XBGFScope::innt(str x)) = "innt(<x>)";
 str pp(XBGFScope::notinnt(str x)) = "notinnt(<x>)";
 str pp(XBGFScope::comboscope(XBGFScope w1, XBGFScope w2)) = "comboscope(<pp(w1)>,<pp(w2)>)";
 default str pp(XBGFScope smth) = "??<smth>??";
+
+str pp(list[str] ss) = joinStrings(ss,",");

shared/rascal/src/mutate/Subgrammar.rsc

@@ -0,0 +1,20 @@
+@contributor{Vadim Zaytsev - vadim@grammarware.net - SWAT, CWI}
+module mutate::Subgrammar
+
+import syntax::BGF;
+import transform::library::Util;
+
+public BGFGrammar subgrammar(BGFGrammar g, str root)
+{
+	BGFProdList ps = [];
+	set[str] covered = {}, uncovered = {root};
+	for(str nt <- uncovered)
+	{
+		newps = [p | p:production(_,nt,_) <- g.prods];
+		newnts = {n | /nonterminal(n) := newps};
+		ps += newps;
+		covered += newnts;
+		uncovered -= nt;
+	}
+	return grammar([root],ps);
+}