/// <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>
/// Creates a new scope for calling a function and populates values for parameters passed to the function.
/// </summary>
/// <param name="function">The function defining the parameters to populate.</param>
/// <param name="scope">The outer scope containing the function call.</param>
/// <param name="error">[out] A <see cref="ParseErrorExpression"/> indicating why constructing the new scope failed.</param>
/// <returns>The new scope, <c>null</c> if an error occurred - see <paramref name="error"/> for error details.</returns>
public InterpreterScope GetParameters(FunctionDefinitionExpression function, InterpreterScope scope, out ExpressionBase error)
{
var parameterScope = new InterpreterScope(scope);
var providedParameters = new List <string>(function.Parameters.Count);
foreach (var parameter in function.Parameters)
{
providedParameters.Add(parameter.Name);
}
ArrayExpression varargs = null;
if (providedParameters.Remove("..."))
{
varargs = new ArrayExpression();
parameterScope.AssignVariable(new VariableExpression("varargs"), varargs);
}
var parameterCount = providedParameters.Count;
int index = 0;
bool namedParameters = false;
foreach (var parameter in Parameters)
{
var assignedParameter = parameter as AssignmentExpression;
if (assignedParameter != null)
{
if (!providedParameters.Remove(assignedParameter.Variable.Name))
{
if (!function.Parameters.Any(p => p.Name == assignedParameter.Variable.Name))
{
error = new ParseErrorExpression(String.Format("'{0}' does not have a '{1}' parameter", function.Name.Name, assignedParameter.Variable.Name), parameter);
return(null);
}
error = new ParseErrorExpression(String.Format("'{0}' already has a value", assignedParameter.Variable.Name), assignedParameter.Variable);
return(null);
}
var assignmentScope = new InterpreterScope(scope)
{
Context = assignedParameter
};
ExpressionBase value;
if (!assignedParameter.Value.ReplaceVariables(assignmentScope, out value))
{
error = new ParseErrorExpression(value, assignedParameter.Value);
return(null);
}
assignedParameter.Value.CopyLocation(value);
parameterScope.DefineVariable(new VariableDefinitionExpression(assignedParameter.Variable), value);
namedParameters = true;
}
else
{
if (namedParameters)
{
error = new ParseErrorExpression("Non-named parameter following named parameter", parameter);
return(null);
}
if (index >= parameterCount && varargs == null)
{
error = new ParseErrorExpression("Too many parameters passed to function", parameter);
return(null);
}
var variableName = (index < parameterCount) ? function.Parameters.ElementAt(index).Name : "...";
var assignmentScope = new InterpreterScope(scope)
{
Context = new AssignmentExpression(new VariableExpression(variableName), parameter)
};
ExpressionBase value;
if (!parameter.ReplaceVariables(assignmentScope, out value))
{
error = new ParseErrorExpression(value, parameter);
return(null);
}
parameter.CopyLocation(value);
if (index < parameterCount)
{
providedParameters.Remove(variableName);
parameterScope.DefineVariable(new VariableDefinitionExpression(variableName), value);
}
else
{
varargs.Entries.Add(value);
}
}
++index;
}
foreach (var parameter in providedParameters)
{
ExpressionBase value;
if (!function.DefaultParameters.TryGetValue(parameter, out value))
{
error = new ParseErrorExpression(String.Format("Required parameter '{0}' not provided", parameter), FunctionName);
return(null);
}
var assignmentScope = new InterpreterScope(scope)
{
Context = new AssignmentExpression(new VariableExpression(parameter), value)
};
if (!value.ReplaceVariables(assignmentScope, out value))
{
error = new ParseErrorExpression(value, this);
return(null);
}
parameterScope.DefineVariable(new VariableDefinitionExpression(parameter), value);
}
error = null;
return(parameterScope);
}