private void GenerateStatement(Expression pStatement, Type pExpectedType)
{
if (pStatement is DeclareVar)
{
DeclareVar curStmnt = (DeclareVar)pStatement;
DeclareSymbolInTable(curStmnt.Identifier, curStmnt.GetSystemType());
}
else if (pStatement is ReadInt)
{
ReadInt curStmnt = (ReadInt)pStatement;
_ilGenerator.Emit(Emit.OpCodes.Call, GetMSILMethod("ReadLine", typeof(String)));
_ilGenerator.Emit(Emit.OpCodes.Call, GetMSILMethod("Parse", typeof(Int32)));
ValidateSymbolType(curStmnt._Identifier, typeof(Int32));
_ilGenerator.Emit(Emit.OpCodes.Stloc, GetValueFromSymbolTable(curStmnt._Identifier, -1));
}
else if (pStatement is StringLiteral)
{
StringLiteral curStmnt = (StringLiteral)pStatement;
_ilGenerator.Emit(Emit.OpCodes.Ldstr, curStmnt._Value);
if (pExpectedType != typeof(String))
{
throw new Exception("can't coerce a " + typeof(Int32).Name + " to a " + pExpectedType.Name);
}
}
else if (pStatement is IntLiteral)
{
IntLiteral curStmnt = (IntLiteral)pStatement;
//Sample ASM: IL_0001: ldc.i4.3 (pushes 3 onto stack)
_ilGenerator.Emit(Emit.OpCodes.Ldc_I4, curStmnt._Value);
//Casting Possibility
if (pExpectedType != typeof(Int32))
{
if (pExpectedType == typeof(String))
{
_ilGenerator.Emit(Emit.OpCodes.Box, typeof(Int32));
_ilGenerator.Emit(Emit.OpCodes.Callvirt, GetMSILMethod("toString", null));
}
else
{
throw new Exception("can't coerce a " + typeof(Int32).Name + " to a " + pExpectedType.Name);
}
}
}
else if (pStatement is Variable)
{
Variable curStmnt = (Variable)pStatement;
_ilGenerator.Emit(Emit.OpCodes.Ldloc, GetValueFromSymbolTable(curStmnt._Identifier, -1));
if (pExpectedType != TypeOfExpression(pStatement))
{
if (TypeOfExpression(pStatement) == typeof(Int32) && pExpectedType == typeof(String))
{
_ilGenerator.Emit(Emit.OpCodes.Box, typeof(Int32));
_ilGenerator.Emit(Emit.OpCodes.Callvirt, GetMSILMethod("toString", null));
}
else
{
throw new Exception("can't coerce a " + TypeOfExpression(pStatement).Name +
" to a " + pExpectedType.Name);
}
}
}
else if (pStatement is LinkedList)
{
LinkedList seq = (LinkedList)pStatement;
GenerateStatement(seq.First, null);
GenerateStatement(seq.Second, null);
}
else if (pStatement is Assign)
{
//retrieve info about variable, including address, type
//LHS addrs <--addr;
//LHS type <-- type;
//getToken();
//match(TK_ASSIGN);
//a = b+c;
//push b
//push c
//add
//pop a
Assign curStmnt = (Assign)pStatement;
GenerateStatement(curStmnt._Expression, TypeOfExpression(curStmnt._Expression));
//ValidateSymbolType(curStmnt._Identifier, TypeOfExpression(curStmnt._Expression));
//Pops the current value from the top of the evaluation stack and stores it in a the local variable list at index 0.
_ilGenerator.Emit(Emit.OpCodes.Stloc, GetValueFromSymbolTable(curStmnt._Identifier, -1));
}
else if (pStatement is Print)
{
Print curStmnt = (Print)pStatement;
GenerateStatement(curStmnt._Expr, TypeOfExpression(curStmnt._Expr));
_ilGenerator.Emit(Emit.OpCodes.Call, GetMSILMethod("Print", TypeOfExpression(curStmnt._Expr)));
}
else if (pStatement is ForLoop)
{
ForLoop curStmnt = (ForLoop)pStatement;
Assign assign = new Assign(curStmnt._Identifier, curStmnt._From, -1);
GenerateStatement(assign, null);
// jump to the test
Emit.Label test = _ilGenerator.DefineLabel();
Emit.Label body = _ilGenerator.DefineLabel();
_ilGenerator.Emit(Emit.OpCodes.Br, test);
_ilGenerator.MarkLabel(body);
GenerateStatement(curStmnt._Body, null);
// to (increment the value of x)
_ilGenerator.Emit(Emit.OpCodes.Ldloc, GetValueFromSymbolTable(curStmnt._Identifier, -1));
_ilGenerator.Emit(Emit.OpCodes.Ldc_I4, 1);
_ilGenerator.Emit(Emit.OpCodes.Add);
ValidateSymbolType(curStmnt._Identifier, typeof(Int32));
_ilGenerator.Emit(Emit.OpCodes.Stloc, GetValueFromSymbolTable(curStmnt._Identifier, -1));
_ilGenerator.MarkLabel(test);
_ilGenerator.Emit(Emit.OpCodes.Ldloc, GetValueFromSymbolTable(curStmnt._Identifier, -1));
GenerateStatement(curStmnt._To, typeof(Int32));
_ilGenerator.Emit(Emit.OpCodes.Blt, body);
}
else
{
throw new Exception("don't know how to generate a " + pStatement.GetType().Name);
}
}