/// <summary>
/// Appends a TType to this TArgumentList. If a TArgumentList is passed, then the values contained in that
/// TArgumentList are appended to this TArgumentList. If the values to be appended are TVariables, then the
/// value of the TVariable will be appended instead of the TVariable itself (although if TVariable A
/// containing TVariable B is passed, then TVariable B will be appended, as opposed to TVariable B's value).
/// </summary>
/// <param name="argument">The TType to append.</param>
public void Add(TType argument)
{
TArgumentList argList = argument as TArgumentList;
if (argList == null)
{
TVariable variable = argument as TVariable;
if (variable == null)
{
arguments.Add(argument);
}
else
{
arguments.Add(variable.Value);
}
}
else
{
for (int i = 0; i < argList.Count; ++i)
{
arguments.Add(argList[i]);
}
}
}
/// <summary>
/// Calls the TFunction with the specified arguments.
/// </summary>
/// <param name="interpreter">The interpreter that the method is being called from.</param>
/// <param name="value">
/// The argument to pass to the function. When passing multiple arguments, use a TArgumentList.
/// </param>
/// <returns></returns>
public TType Call(Interpreter interpreter, TType value)
{
// If value is already a TArgumentList, then simply copy the reference, otherwise create a new
// TArgumentList and add the value to it. This TArgument list is to be passed to the function.
TArgumentList argList = value as TArgumentList;
if (argList == null)
{
argList = new TArgumentList();
argList.Add(value);
}
// If the function takes a fixed number of arguments...
if (ArgNames != null)
{
// Occupy the argument list with the default arguments. If there is no default argument in a place
// where an argument should have been given, return a TException.
if (argList.Count < ArgNames.Length)
{
for (int i = argList.Count; i < DefaultArgs.Length; ++i)
{
if (DefaultArgs[i] == null)
{
break;
}
else
{
argList.Add(DefaultArgs[i]);
}
}
}
if (argList.Count != ArgNames.Length)
{
return(new TException(interpreter, "Incorrect number of arguments for function '" + Name + "'",
argList.Count.ToString() + " out of " + ArgNames.Length.ToString() + " given"));
}
}
interpreter.Stack.Push();
// Keep a track of the new stack level so that if a function calls 'exit()', which pops from the stack,
// this will be able to be detected and the function call can be terminated properly
int stackLevel = interpreter.Stack.Level;
// Put the arguments on the current stack 'frame'
if (ArgNames == null)
{
for (int i = 0; i < argList.Count; ++i)
{
interpreter.Stack.AddVariable(new TVariable("arg" + i.ToString(), argList[i]));
}
}
else
{
for (int i = 0; i < argList.Count; ++i)
{
interpreter.Stack.AddVariable(new TVariable(ArgNames[i], argList[i]));
}
}
TType returnValue = null;
bool dontPop = false; // Set to true if the stack is popped during the call, i.e. if 'exit()' is called
// Call the function
if (HardCodedFunction != null)
{
returnValue = HardCodedFunction.Invoke(interpreter, argList);
}
else if (Block != null)
{
bool breakUsed;
returnValue = Block.Execute(interpreter, out dontPop, out breakUsed);
}
else if (CustomFunction != "")
{
returnValue = interpreter.Interpret(CustomFunction, true);
if (interpreter.Stack.Level < stackLevel)
{
dontPop = true;
}
}
// If returnValue is a TVariable, then return the value of the TVariable (e.g. we want to return 5, as
// opposed to the variable X which contains 5)
TVariable variable = returnValue as TVariable;
if (variable != null)
{
returnValue = variable.Value;
}
if (!dontPop)
{
interpreter.Stack.Pop();
}
return(returnValue ?? TNil.Instance);
}
/// <summary>
/// Adds a variable within the current Toast function's scope.
/// </summary>
/// <param name="variable">The TVariable to add.</param>
public void AddVariable(TVariable variable)
{
stack.Peek().Add(variable.Identifier, variable);
}
/// <summary>
/// Parses an assignment operation.
/// </summary>
/// <param name="group">The group to parse.</param>
/// <returns>The assigned variable or function on success, otherwise a TException.</returns>
TType ParseAssignmentGroup(Group group)
{
/* BNF for assignment:
* <assignment> ::= 'let' ( <variable-assignment> | <function-declaration> )
* <var-assignment> ::= <identifier> '=' <expression>
* <func-declaration> ::= <identifier> '(' { <parameters> } ')' '=' <statements>
* <parameters> ::= <identifier> { ',' <identifier> }*
* <statements> ::= <block> | <statement>
* <block> ::= <new-line> (<statement> <new-line>)* 'end'
* You can probably guess what <identifier>, <statement> and <new-line> are
* The 'let' is assumed to have already been checked for
*/
int equalsIndex = group.IndexOf("=");
if (equalsIndex < 0) return new TException(this, "Variable or function could not be assigned a value");
// Could be assigning a dereferenced variable
TException exception = ParseReferencesOfGroup(group, equalsIndex);
if (exception != null) return exception;
if (group.Count == 1) return new TException(this, "Could not assign variable", "no variable name given");
string variableName = group[1] as string;
TVariable existingVariable = null;
if (variableName == null)
{
exception = new TException(this, "Could not assign variable", "invalid variable name given");
// Check if an existing variable or function is being assigned
Group groupToParse = group[1] as Group;
TType value = group[1] as TType;
if (groupToParse != null) value = ParseGroup(groupToParse);
if (value == null) return exception;
TVariable variable = value as TVariable;
if (variable != null) existingVariable = variable;
else
{
TFunction function = value as TFunction;
if (function != null) variableName = function.Name;
else return exception;
}
}
if (group.Count == 2) return new TException(this, "Variable could not be assigned a value");
string assignmentOperator = group[2] as string;
if (assignmentOperator == null) // Now we assume that we're dealing with a function declaration
{
Group paramGroup = group[2] as Group;
if (paramGroup == null) // The user probably just wanted to assign a variable but made a typo
return new TException(this, "Variable could not be assigned a value",
"value to assign to variable must be given");
// Get the identifiers of all the parameters within the brackets, keeping strict watch on comma usage
TParameterList paramList = new TParameterList();
bool commaExpected = false;
for (int i = 0; i < paramGroup.Count; ++i)
{
if (commaExpected && (i == paramGroup.Count - 1))
return new TException(this, "Parameters could not be parsed", "last parameter missing");
string paramName = paramGroup[i] as string;
if (commaExpected && (paramName != ",")) paramName = null;
if (paramName == null) return new TException(this, "Parameters could not be parsed",
"invalid parameter name given");
if (!commaExpected) paramList.Add(paramName);
commaExpected = !commaExpected;
}
exception = new TException(this, "Function could not be given a body", "function body must be given");
if (group.Count == 3) return exception;
assignmentOperator = group[3] as string;
if (assignmentOperator == null) return exception;
else if (assignmentOperator != "=") return exception;
TFunction function;
if (group.Count == 4) // statement is just 'let <i><params> =', so get a block
{
TBlock block = new TBlock(this, out exception, false);
if (exception != null) return exception;
function = new TFunction(variableName ?? existingVariable.Identifier, block,
paramList.ParameterNames, null);
}
else // Create a single line function
{
Group funcBody = new Group(null);
funcBody.AddRange(group.GetRange(4, group.Count - 4));
function = new TFunction(variableName ?? existingVariable.Identifier, funcBody.ToString(),
paramList.ParameterNames, null);
}
exception = TFunction.AddFunction(this, function);
if (exception != null) return exception;
return function;
}
{ // Assume that we're dealing with a variable assigment
exception = new TException(this, "Variable could not be assigned a value",
"value to assign to variable must be given");
if (assignmentOperator != "=") return exception;
if (group.Count == 3) return exception;
// Parse the expression on the right hand side of the assigment operator, and if the result is a
// TVariable, then get it's value (we don't want to assign the TVariable itself to the new TVariable)
Group valueGroup = new Group(null);
valueGroup.AddRange(group.GetRange(3, group.Count - 3));
TType value = ParseGroup(valueGroup);
if (value is TException) return value;
TVariable variable = value as TVariable;
if (variable != null) value = variable.Value;
// Make sure we don't get any circular references; they cause stack overflows when outputting them
variable = existingVariable ?? Stack.FindVariable(variableName);
if (value == variable) return new TException(this, "Illegal assignment attempted",
"variables cannot reference themselves");
TVariable circularRefCheckVar = value as TVariable;
while (circularRefCheckVar != null)
{
TVariable variableValue = circularRefCheckVar.Value as TVariable;
if (variableValue != null)
{
if (variableValue == variable)
return new TException(this, "Illegal assignment attempted",
"circular reference detected");
else circularRefCheckVar = variableValue;
}
else circularRefCheckVar = null;
}
if (variable == null) // If the variable doesn't exist already, add it to the stack variable dictionary
{
variable = new TVariable(variableName, value);
Stack.AddVariable(variable);
}
else variable.Value = value;
return variable;
}
}
/// <summary>
/// Parses a group, searching for any reference and dereference operators. Operators and operands are
/// replaced with the reference/dereferenced value.
/// </summary>
/// <param name="group">The group to parse.</param>
/// <param name="limit">The index of the group to parse up to. Used by the ParseAssignmentGroup method.</param>
/// <returns>A TException on failure, otherwise null.</returns>
TException ParseReferencesOfGroup(Group group, int limit = -1)
{
int limitToUse = limit < 0 ? group.Count - 1 : limit;
int index;
while (true)
{
// Search from right to left for the first reference or dereference character
int refIndex = group.LastIndexOf(TType.REFERENCE_CHARACTER.ToString(), limitToUse),
derefIndex = group.LastIndexOf(TType.DEREFERENCE_CHARACTER.ToString(), limitToUse);
char character; // Used so we know what operation we're carrying out later
if (refIndex < 0)
{
index = derefIndex;
character = TType.DEREFERENCE_CHARACTER;
}
else if (derefIndex < 0)
{
index = refIndex;
character = TType.REFERENCE_CHARACTER;
}
else
{
if (refIndex > derefIndex)
{
index = refIndex;
character = TType.REFERENCE_CHARACTER;
}
else
{
index = derefIndex;
character = TType.DEREFERENCE_CHARACTER;
}
}
if (index < 0) break;
if (index + 1 > group.Count)
return new TException(this, "Invalid expression term '" + character + "' at end of statement");
// If the operand is not a variable, return a TException (can't dereference values)
TType variable = TType.Parse(this, group[index + 1]);
if (variable is TException) return variable as TException;
if (!(variable is TVariable))
{
if (character == TType.REFERENCE_CHARACTER)
return new TException(this,
"Attempted creation of reference to value", "expected variable identifier");
else
return new TException(this, "Attempted dereference of value", "expected variable identifier");
}
if (character == TType.REFERENCE_CHARACTER) group[index] = new TVariable("reference", variable);
else
{
group[index] = ((TVariable)variable).Value;
if (!(group[index] is TVariable) && !(group[index] is TFunction))
return new TException(this,
"Dereference of value type variable", "expected reference");
}
group.RemoveAt(index + 1);
limitToUse = limit < 0 ? group.Count - 1 : limit;
}
return null;
}