/// <summary>
/// Updates the provided scope with the new variable value.
/// </summary>
/// <param name="scope">The scope object containing variable values and function parameters.</param>
/// <returns>
/// <c>null</c> if successful, or a <see cref="ParseErrorExpression" /> if not.
/// </returns>
public ParseErrorExpression Evaluate(InterpreterScope scope)
{
var assignmentScope = new InterpreterScope(scope)
{
Context = this
};
ExpressionBase result;
var functionDefinition = Value as FunctionDefinitionExpression;
if (functionDefinition != null)
{
scope.AddFunction(functionDefinition);
result = new FunctionReferenceExpression(functionDefinition.Name.Name);
}
else
{
if (!Value.ReplaceVariables(assignmentScope, out result))
{
return((ParseErrorExpression)result);
}
}
return(scope.AssignVariable(Variable, result));
}
/// <summary>
/// Replaces the variables in the expression with values from <paramref name="scope" />.
/// </summary>
/// <param name="scope">The scope object containing variable values.</param>
/// <param name="result">[out] The new expression containing the replaced variables.</param>
/// <returns>
/// <c>true</c> if substitution was successful, <c>false</c> if something went wrong, in which case <paramref name="result" /> will likely be a <see cref="ParseErrorExpression" />.
/// </returns>
public override bool ReplaceVariables(InterpreterScope scope, out ExpressionBase result)
{
ExpressionBase value = scope.GetVariable(Name);
if (value == null)
{
var func = scope.GetFunction(Name);
if (func != null)
{
// special wrapper for returning a function as a variable
result = new FunctionReferenceExpression(Name);
result.CopyLocation(this);
return(true);
}
result = new UnknownVariableParseErrorExpression("Unknown variable: " + Name, this);
return(false);
}
return(value.ReplaceVariables(scope, out result));
}
