Expression *ScriptManager::BuildExpression(ifstream &in)
{
ExprType type = (ExprType)0;
in.read((char *)&type, 1);
ExprOp op = (ExprOp)0;
string varName = "";
Expression *lhs = 0, *rhs = 0;
switch(type)
{
case EXPR_LITERAL:
int value;
in.read((char *)&value, 4);
return new ExprLiteral(value);
case EXPR_VAR:
getline(in, varName, '\0');
return new ExprVar(varName);
case EXPR_UNARY_OP:
in.read((char *)&op, 1);
return new ExprUnaryOp(op, BuildExpression(in));
case EXPR_BINARY_OP:
in.read((char *)&op, 1);
lhs = BuildExpression(in);
rhs = BuildExpression(in);
return new ExprBinaryOp(op, lhs, rhs);
default:
string oops = "Invalid opcode: ";
oops += (char)type;
throw ExprParseException(oops);
}
}
BOOL CCalculator::Expression(CCalcExpression** ppcExpression)
{
BOOL bOperator;
BOOL bOperand;
BOOL bFirst;
CArrayIntAndPointer cArray;
CCalcOperator* pcOperator;
CCalcExpression* pcOperand;
cArray.Init(16);
bFirst = TRUE;
for (;;)
{
for (;;)
{
bOperator = Operator(&pcOperator);
if (!bOperator)
{
break;
}
cArray.Add(pcOperator, 0);
}
bOperand = Operand(&pcOperand);
if (!bOperand && !bOperator)
{
if (bFirst)
{
cArray.Kill();
return FALSE;
}
else
{
BuildExpression(ppcExpression, &cArray);
cArray.Kill();
if (*ppcExpression == NULL)
{
return FALSE;
}
else
{
return TRUE;
}
}
}
cArray.Add(pcOperand, 0);
bFirst = FALSE;
}
}
//-----------------------------------------------------------------------------
// Interface to solve a conditional expression. Returns false on failure.
//-----------------------------------------------------------------------------
bool EvaluateExpression( bool &result, const char *InfixExpression, GetSymbolProc_t pGetSymbolProc )
{
if ( !InfixExpression )
return false;
g_pGetSymbolProc = pGetSymbolProc;
bool success = false;
mExpression = InfixExpression;
mExprTree = 0;
mCurPosition = 0;
// Building the expression tree will fail on bad syntax
if ( BuildExpression() )
{
success = true;
result = SimplifyNode( mExprTree );
}
FreeTree( mExprTree );
return success;
}