private void ExecuteForStmt(Ast.ForStmt stmt, ScriptEnv env)
{
var firstNumber = EvaluateExpr <long>(stmt.FirstNumberExpr, env);
var lastNumber = EvaluateExpr <long>(stmt.LastNumberExpr, env);
long step = firstNumber <= lastNumber ? 1 : -1;
if (stmt.StepExpr != null)
{
step = EvaluateExpr <long>(stmt.StepExpr, env);
}
if (step == 0)
{
throw new ScriptException("The STEP value in a FOR statement must not be zero.");
}
else if (step < 0 && firstNumber < lastNumber)
{
throw new ScriptException(
"The STEP value in a FOR statement must be positive if \"first-number\" < \"last-number\".");
}
else if (step > 0 && firstNumber > lastNumber)
{
throw new ScriptException(
"The STEP value in a FOR statement must be negative if \"first-number\" > \"last-number\".");
}
var upward = step > 0;
long counter = firstNumber;
while ((upward && counter <= lastNumber) || (!upward && counter >= lastNumber))
{
env.Vars[stmt.VariableName] = counter;
ExecuteBlock(stmt.Block, env);
if (env.DidReturn || env.DidThrow)
{
return;
}
else if (env.DidBreak)
{
env.DidBreak = false;
break;
}
else if (env.DidContinue)
{
env.DidContinue = false;
}
counter += step;
}
}
private Ast.Stmt ParseForStmt(TokenQueue q)
{
var stmt = new Ast.ForStmt {
SourceToken = q.SourceToken
};
q.Take("for");
stmt.VariableName = ParseVariableName(q);
q.Take("=");
stmt.FirstNumberExpr = ParseExpr(q);
q.Take("to");
stmt.LastNumberExpr = ParseExpr(q);
if (q.TakeMaybe("step"))
{
stmt.StepExpr = ParseExpr(q);
}
stmt.Block = ParseBlock(q);
ConsumeSemicolon(q);
return(stmt);
}