/// <summary>
/// Executes an equality instruction between two values
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>The result of the equality</returns>
private KBool Eq(KermitAST tree)
{
KObject a = Execute((KermitAST)tree.GetChild(0));
KObject b = Execute((KermitAST)tree.GetChild(1));
return(a == b);
}
/// <summary>
/// Assign a value to a variable
/// </summary>
/// <param name="tree">Tree to be executed</param>
private void Assign(KermitAST tree)
{
KermitAST lhs = (KermitAST)tree.GetChild(0);
KermitAST expr = tree.GetChild(1) as KermitAST;
KObject value = Execute(expr);
if (value != null && !value.IsVoid)
{
if (lhs.Type == KermitParser.DOT || lhs.Type == KermitParser.INDEX)
{
FieldAssign(lhs, value);
}
else
{
MemorySpace space = GetSpaceWithSymbol(lhs.Text) ?? _currentSpace;
KLocal var = space[lhs.Text];
if (var == null)
{
space[lhs.Text] = new KLocal(lhs.Text, value);
}
else
{
var.Value = value;
}
}
}
}
/// <summary>
/// Load a field of an object
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>The result of the field</returns>
private KObject FieldLoad(KermitAST tree)
{
KermitAST leftExpr = (KermitAST)tree.GetChild(0);
KermitAST field = (KermitAST)tree.GetChild(1);
KObject obj = Execute(leftExpr);
KObject val;
string name;
if (field.Type == KermitParser.INDEX)
{
field = (KermitAST)field.GetChild(0);
}
if (field.Type == KermitParser.CALL)
{
name = field.GetChild(0).Text;
FunctionSpace fSpace = new FunctionSpace(new FunctionSymbol(leftExpr.Text + "." + name, GlobalScope));
MemorySpace savedSpace = _currentSpace;
_stack.Push(fSpace);
object[] args = new object[field.ChildCount - 1];
for (int i = 0; i < args.Length; ++i)
{
KObject ko = Execute((KermitAST)field.GetChild(i + 1));
args[i] = obj is KArray ? ko : ko.Value;
}
try
{
_currentSpace = fSpace;
val = obj.CallInnerFunction(name, args);
}
finally
{
_stack.Pop();
_currentSpace = savedSpace;
}
}
else
{
name = field.Text;
val = obj.GetInnerField(name);
}
field = (KermitAST)field.Parent;
if (field.Type == KermitParser.INDEX)
{
KermitAST memberTree = (KermitAST)field.GetChild(1);
val = LoadItem(val, Execute(memberTree));
if (val == null)
{
ThrowHelper.TypeError($"'{name}' is not enumerable", StackTrace);
}
}
if (val == null)
{
ThrowHelper.NoFieldError(obj.Value.GetType().Name, name, StackTrace);
}
return(val);
}
/// <summary>
/// Adds two values.
/// - If both are numbers, executes the arithmetic operation
/// - If one of them is a string, then the two string representations are concatenated
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>The result of the execution</returns>
private KObject Add(KermitAST tree)
{
KObject a = Execute((KermitAST)tree.GetChild(0));
KObject b = Execute((KermitAST)tree.GetChild(1));
if (a.IsString || b.IsString)
{
return(new KString(a.Value + b.Value.ToString()));
}
return(Arithmetic(tree));
}
/// <summary>
/// Load an item from an enumerable object
/// </summary>
/// <param name="tree">The tree to be executed</param>
/// <returns>The loaded object</returns>
private KObject LoadItem(KermitAST tree)
{
KermitAST expr = (KermitAST)tree.GetChild(0);
KermitAST memberTree = (KermitAST)tree.GetChild(1);
KObject res = LoadItem(Execute(expr), Execute(memberTree));
if (res == null)
{
ThrowHelper.TypeError($"'{expr.Text}' is not enumerable", StackTrace);
}
return(res);
}
/// <summary>
/// Compares two values if they are IComparable
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>The result of the comparison</returns>
private int Compare(KermitAST tree)
{
KObject a = Execute((KermitAST)tree.GetChild(0));
KObject b = Execute((KermitAST)tree.GetChild(1));
if (a.Is <IComparable>() && b.Is <IComparable>())
{
return(((IComparable)a).CompareTo(b));
}
string name = a.Is <IComparable>() ? b.GetType().Name : a.GetType().Name;
ThrowHelper.TypeError($"Type {name} is not comparable");
return(-1);
}
/// <summary>
/// Call a function
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>The result of the function</returns>
private KObject Call(KermitAST tree)
{
string fName = tree.GetChild(0).Text;
KFunction function = GetFunction(fName);
if (function == null)
{
ThrowHelper.NameNotExists(fName, StackTrace);
//Listener.Error($"Function name {fName} is not defined");
return(null);
}
int argCount = tree.ChildCount - 1;
if (!function.IsNative &&
(function.Value.Arguments == null && argCount > 0 ||
function.Value.Arguments != null && argCount != function.Value.Arguments.Count))
{
ThrowHelper.TypeError($"Function {fName} takes {argCount} arguments", StackTrace);
//Listener.Error($"Function {fName}: argument list mismatch");
return(null);
}
List <KLocal> param = new List <KLocal>(argCount);
var arguments = function.Value.Arguments.Values.GetEnumerator();
for (int i = 0; i < argCount; ++i)
{
arguments.MoveNext();
string name = function.IsNative ? "" : arguments.Current.Name;
KermitAST argumentTree = (KermitAST)tree.GetChild(i + 1);
KLocal var;
if (argumentTree.Type == KermitParser.REF)
{
var = new KGlobal(name, argumentTree.GetChild(0).Text, _currentSpace);
}
else
{
KObject argumentValue = Execute(argumentTree);
var = new KLocal(name, argumentValue);
}
param.Add(var);
}
return(CallFunction(function, param));
}
/// <summary>
/// Executes an if statement
/// </summary>
/// <param name="tree">Tree to be executed</param>
private void IfStatement(KermitAST tree)
{
KermitAST condition = (KermitAST)tree.GetChild(0);
KermitAST code = (KermitAST)tree.GetChild(1);
KermitAST elseCode = tree.ChildCount == 3 ? (KermitAST)tree.GetChild(2) : null;
KBool cres = TypeHelper.ToBool(Execute(condition));
if (cres)
{
Execute(code);
}
else if (elseCode != null)
{
Execute(elseCode);
}
}
/// <summary>
/// Assign a value to a field
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <param name="value">Value to be set</param>
private void FieldAssign(KermitAST tree, KObject value)
{
KermitAST leftExpr = (KermitAST)tree.GetChild(0);
KermitAST field = (KermitAST)tree.GetChild(1);
KObject obj = Execute(leftExpr);
bool isTree = tree.Type == KermitParser.INDEX || field.Type == KermitParser.INDEX;
if (field.Type == KermitParser.INDEX)
{
obj = obj.GetInnerField(field.GetChild(0).Text);
field = (KermitAST)field.GetChild(1);
}
if (isTree)
{
object fieldValue = Execute(field).Value;
if (obj is KArray)
{
((KArray)obj)[(int)fieldValue] = value;
}
else
{
object real = obj.Value;
Type objType = real.GetType();
MethodInfo info = objType.GetMethod("set_Item");
if (info != null)
{
info.Invoke(real, new[] { fieldValue, value.Value });
}
else
{
ThrowHelper.AttributeError($"{leftExpr.Text} is not asignable", StackTrace);
}
}
}
else if (tree.Type == KermitParser.DOT)
{
string name = field.Text;
if (!obj.SetInnerField(name, value))
{
ThrowHelper.NoFieldError(obj.Value.GetType().Name, name, StackTrace);
}
}
}
/// <summary>
/// Print the result of the node execution to the console if in REPL mode
/// </summary>
/// <param name="tree">Tree to be executed</param>
private void ReplPrint(KermitAST tree)
{
KermitAST exec = (KermitAST)tree.GetChild(0);
KObject obj = Execute(exec);
if (ReplMode && obj != null && !(obj is KVoid))
{
Listener.Write(obj.ToString());
}
}
/// <summary>
/// Performs a while loop
/// </summary>
/// <param name="tree">Tree to be executed</param>
private void WhileLoop(KermitAST tree)
{
KermitAST condition = (KermitAST)tree.GetChild(0);
KermitAST code = (KermitAST)tree.GetChild(1);
ScopeSpace sp = new ScopeSpace("while", _currentSpace);
MemorySpace save = _currentSpace;
try
{
_currentSpace = sp;
KBool cond = Execute(condition).Cast <KBool>();
while (cond)
{
Execute(code);
cond = Execute(condition).Cast <KBool>();
}
}
finally
{
_currentSpace = save;
}
}
/// <summary>
/// Performs a for loop
/// </summary>
/// <param name="tree">Tree to be executed</param>
private void ForLoop(KermitAST tree)
{
KermitAST begin = (KermitAST)tree.GetChild(0);
KermitAST condition = (KermitAST)tree.GetChild(1);
KermitAST action = (KermitAST)tree.GetChild(2);
KermitAST code = (KermitAST)tree.GetChild(3);
ScopeSpace sp = new ScopeSpace("while", _currentSpace);
MemorySpace save = _currentSpace;
try
{
_currentSpace = sp;
for (Execute(begin); (KBool)Execute(condition); Execute(action))
{
Execute(code);
}
}
finally
{
_currentSpace = save;
}
}
/// <summary>
/// Instance an object
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>The instantiated object</returns>
private KObject Instance(KermitAST tree)
{
KermitAST objName = (KermitAST)tree.GetChild(0);
Symbol s = objName.Scope.Resolve(objName.Text);
if (s is NativeSymbol)
{
object[] args = tree.Children.Skip(1).Select(x => Execute((KermitAST)x).Value).ToArray();
return(InstantiateObject(s as NativeSymbol, args));
}
ThrowHelper.NameNotExists(objName.Text, StackTrace);
return(null);
}
/// <summary>
/// Performs an arithmetic operation over two values
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>The result of the execution</returns>
private KObject Arithmetic(KermitAST tree)
{
KNumber a = Execute((KermitAST)tree.GetChild(0)).Cast <KNumber>();
KNumber b = Execute((KermitAST)tree.GetChild(1)).Cast <KNumber>();
switch (tree.Type)
{
case KermitParser.ADD:
return(a + b);
case KermitParser.SUB:
return(a - b);
case KermitParser.MUL:
return(a * b);
case KermitParser.DIV:
return(a / b);
}
// We shouldn't reach this fragment
ThrowHelper.TypeError($"Unsupported arithmetic operation {tree.Text}");
return(null);
}
/// <summary>
/// Main interpreter method.
/// This method distributes all node types to the corresponding functions to be executed
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>An object or null, the result of the execution</returns>
/// <exception cref="InterpreterException">If an internal error occurs</exception>
private KObject Execute(KermitAST tree)
{
try
{
switch (tree.Type)
{
case KermitParser.RPRINT:
ReplPrint(tree);
break;
case KermitParser.BLOCK:
Block(tree);
break;
case KermitParser.ASSIGN:
Assign(tree);
break;
case KermitParser.IF:
IfStatement(tree);
break;
case KermitParser.WHILE:
WhileLoop(tree);
break;
case KermitParser.FOR:
ForLoop(tree);
break;
case KermitParser.RETURN:
Return(tree);
break;
case KermitParser.CALL:
return(Call(tree));
case KermitParser.NEW:
return(Instance(tree));
case KermitParser.ARR:
return(CreateArray(tree));
// Arithmetic operations
case KermitParser.ADD:
return(Add(tree));
case KermitParser.SUB:
case KermitParser.MUL:
case KermitParser.DIV:
return(Arithmetic(tree));
// Logic operations
case KermitParser.EQ:
return(Eq(tree));
case KermitParser.NE:
return((KBool) !Eq(tree));
case KermitParser.LT:
return(Lt(tree));
case KermitParser.BT:
return(Bt(tree));
case KermitParser.LTE:
return((KBool) !Bt(tree));
case KermitParser.BTE:
return((KBool) !Lt(tree));
case KermitParser.NOT:
return(Not(tree));
// Keep types at the bottom
case KermitParser.TRUE:
return(KBool.True);
case KermitParser.FALSE:
return(KBool.False);
case KermitParser.NUM:
return((KNumber)Execute((KermitAST)tree.GetChild(0)) * (tree.ChildCount == 2 ? -1 : 1));
case KermitParser.INT:
return((KInt)int.Parse(tree.Text));
case KermitParser.CHAR:
return((KChar)tree.Text[1]);
case KermitParser.FLOAT:
return((KFloat)float.Parse(tree.Text));
case KermitParser.STRING:
return((KString)tree.Text.Substring(1, tree.Text.Length - 2));
// Accessors
case KermitParser.INDEX:
case KermitParser.DOT:
case KermitParser.ID:
return(Load(tree));
default:
throw new InvalidOperationException("Node " + tree.Text + "<" + tree.Type + "> not handled");
}
}
catch (InterpreterException e) when(e.CallStack == null)
{
e.CallStack = StackTrace;
throw;
}
catch (Exception e) when(!(e is InterpreterException || e is ReturnValue))
{
ThrowHelper.InterpreterException(e.Message, e, StackTrace);
}
return(null);
}
/// <summary>
/// Interrupts the current block execution and sets the return value
/// </summary>
/// <param name="tree">Tree to be executed</param>
private void Return(KermitAST tree)
{
_sharedReturnValue.Value = Execute((KermitAST)tree.GetChild(0));
throw _sharedReturnValue;
}
/// <summary>
/// Negates an expression
/// </summary>
/// <param name="tree">Tree to be executed</param>
/// <returns>The negated expression</returns>
private KBool Not(KermitAST tree)
{
KObject inner = Execute((KermitAST)tree.GetChild(0));
return(!inner);
}