From b94c42ae4a17aef75fc0ac8b4d98a7342031cba4 Mon Sep 17 00:00:00 2001
From: Joachim Klein <klein@tcs.inf.tu-dresden.de>
Date: Fri, 13 Oct 2017 15:41:18 +0200
Subject: [PATCH] ExpressionLiteral: support for BigRational literals, use
 string for evaluateExact

---
 prism/src/parser/ast/ExpressionLiteral.java | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/prism/src/parser/ast/ExpressionLiteral.java b/prism/src/parser/ast/ExpressionLiteral.java
index 71338bf7..d088208a 100644
--- a/prism/src/parser/ast/ExpressionLiteral.java
+++ b/prism/src/parser/ast/ExpressionLiteral.java
@@ -34,7 +34,7 @@ import parser.type.*;
 public class ExpressionLiteral extends Expression
 {
 	Object value; // Value
-	String string; // Optionally, keep original string to preserve user formatting
+	String string; // Optionally, keep original string to preserve user formatting and allow exact evaluation
 
 	// Constructor
 	
@@ -92,13 +92,24 @@ public class ExpressionLiteral extends Expression
 	@Override
 	public Object evaluate(EvaluateContext ec) throws PrismLangException
 	{
+		if (value instanceof BigRational) {
+			// cast from BigRational to appropriate Java data type
+			return getType().castFromBigRational((BigRational) value);
+		}
 		return value;
 	}
 
 	@Override
 	public BigRational evaluateExact(EvaluateContext ec) throws PrismLangException
 	{
-		return BigRational.from(value);
+		if (value instanceof BigRational) {
+			// if already a BigRational, return that
+			return (BigRational) value;
+		} else if (value instanceof Boolean) {
+			return BigRational.from(value);
+		}
+		// otherwise, convert from string representation (potentially provides more precision for double literals)
+		return BigRational.from(string);
 	}
 
 	@Override