accumulation: properly print ExpressionAccumulation

prism/src/parser/ast/ExpressionAccumulation.java

@@ -145,15 +145,15 @@ public class ExpressionAccumulation extends Expression
 		
 		ret += symbol.toString();
 		
-		if ( hasRegularExpression() ) { ret += "( Reg:" + regexp.toString() + ")"; }
-		else if ( hasBoundExpression() ) { ret += "(" + bound.toString() + ")"; } 
+		if ( hasRegularExpression() ) { ret += "{ Reg:" + regexp.toString() + "}"; }
+		else if ( hasBoundExpression() ) { ret += "{" + bound.toString() + "}"; } 
 		else throw new RuntimeException("Cannot stringify AccumulationExpression without fragment bounds.");
 		
-		ret += "(" + constraint.toString() + ")";
+		ret += "{" + constraint.toString() + "}";
 		
 		if ( hasRecordSet() ) {
 			String fireOnString = recordSet.stream().map(f -> f.toString()).collect(Collectors.joining(","));
-			ret += "(" + fireOnString + ")";
+			ret += "{" + fireOnString + "}";
 		}
 		
 		if(operand2 != null) { ret += " " + operand2.toString(); }