Add new ASTElement.evaluatePartially() methods.

In particular for a whole State, not just a substate.
Also for just some constants, with no variable values.
Can be used to get an expression symbolically in terms of constants.

prism/src/param/ParamResult.java

@@ -153,7 +153,7 @@ public class ParamResult
 
 				// replace constants in the expression that have a value
 				// with the value
-				exprExpected = (Expression) exprExpected.evaluatePartially(constValues, null);
+				exprExpected = (Expression) exprExpected.evaluatePartially(constValues);
 			}
 		} catch (PrismLangException e) {
 			throw new PrismException("Invalid RESULT specification \"" + strExpected + "\" for property: " + e.getMessage());

prism/src/parser/ast/ASTElement.java

@@ -456,6 +456,16 @@ public abstract class ASTElement
 		return (ASTElement) accept(visitor);
 	}
 
+	/**
+	 * Evaluate partially: replace some constants with actual values. 
+	 * Constants are specified as a Values object.
+	 * Warning: Unlike evaluate(), evaluatePartially() methods modify (and return) the expression. 
+	 */
+	public ASTElement evaluatePartially(Values constantValues) throws PrismLangException
+	{
+		return evaluatePartially(new EvaluateContextValues(constantValues, null));
+	}
+
 	/**
 	 * Evaluate partially: replace some constants and variables with actual values. 
 	 * Constants/variables are specified as Values objects; either can be left null.
@@ -466,6 +476,25 @@ public abstract class ASTElement
 		return evaluatePartially(new EvaluateContextValues(constantValues, varValues));
 	}
 
+	/**
+	 * Evaluate partially: replace variables with actual values, specified as a State object.
+	 * Warning: Unlike evaluate(), evaluatePartially() methods modify (and return) the expression. 
+	 */
+	public ASTElement evaluatePartially(State state) throws PrismLangException
+	{
+		return evaluatePartially(new EvaluateContextState(state));
+	}
+
+	/**
+	 * Evaluate partially: replace variables with actual values, specified as a State object.
+	 * Constant values are supplied as a Values object. 
+	 * Warning: Unlike evaluate(), evaluatePartially() methods modify (and return) the expression. 
+	 */
+	public ASTElement evaluatePartially(Values constantValues, State state) throws PrismLangException
+	{
+		return evaluatePartially(new EvaluateContextState(constantValues, state));
+	}
+
 	/**
 	 * Evaluate partially: replace some variables with actual values. 
 	 * Variables are specified as a State object, indexed over a subset of all variables,