Expr IStatementVisitor <Expr> .Visit(Statement.For statement)
{
var parentScope = scope;
scope = Scope.CreateChild(parentScope);
var step = statement.Step == null
? new Expression.Number(1.0).Visit(this)
: ExprHelpers.ConvertToNumber(context, statement.Step.Visit(this));
var loopVariable = scope.AddLocal(statement.Identifier);
var varVar = Expr.Variable(typeof(double));
var limitVar = Expr.Variable(typeof(double));
var stepVar = Expr.Variable(typeof(double));
var breakConditionExpr = ForLoopBreakCondition(limitVar, stepVar, varVar);
var expr =
Expr.Block(
new[] { loopVariable, varVar, limitVar, stepVar },
Expr.Assign(varVar, ExprHelpers.ConvertToNumber(context, statement.Var.Visit(this))),
Expr.Assign(limitVar, ExprHelpers.ConvertToNumber(context, statement.Limit.Visit(this))),
Expr.Assign(stepVar, step),
ExprHelpers.CheckNumberForNan(varVar, String.Format(ExceptionMessage.FOR_VALUE_NOT_NUMBER, "inital value")),
ExprHelpers.CheckNumberForNan(limitVar, String.Format(ExceptionMessage.FOR_VALUE_NOT_NUMBER, "limit")),
ExprHelpers.CheckNumberForNan(stepVar, String.Format(ExceptionMessage.FOR_VALUE_NOT_NUMBER, "step")),
ForLoop(statement, stepVar, loopVariable, varVar, breakConditionExpr));
scope = parentScope;
return(expr);
}
LoopExpression ForLoop(Statement.For statement, ParameterExpression stepVar, ParameterExpression loopVariable,
ParameterExpression varVar, BinaryExpression breakConditionExpr)
{
var loopExpr =
Expr.Loop(
Expr.Block(
Expr.IfThen(breakConditionExpr, Expr.Break(scope.BreakLabel())),
Expr.Assign(loopVariable, Expr.Convert(varVar, typeof(object))),
Visit(statement.Body),
Expr.AddAssign(varVar, stepVar)),
scope.BreakLabel());
return(loopExpr);
}
public object visitForStmt(Statement.For stmt)
{
var counter = (int)stmt.RangeStart.Accept(this);
var end = (int)stmt.RangeEnd.Accept(this);
while (counter <= end)
{
environment.Assign(stmt.Identifier.Name, counter);
foreach (var statement in stmt.Block)
{
statement.Accept(this);
}
counter++;
}
return(null);
}
public bool visitForStmt(Statement.For stmt)
{
var identifier = stmt.Identifier;
if (!environment.Contains(identifier.Name))
{
ErrorWriter.Write(identifier, "Usage of uninitialized variable '{0}'", identifier.Name);
return(false);
}
if (environment.GetType(identifier.Name) != "int")
{
ErrorWriter.Write(identifier, "Loop variable '{0}' must be of type 'int'", identifier.Name);
return(false);
}
var startType = stmt.RangeStart.Accept(expressionAnalyzer);
if (startType != "int")
{
ErrorWriter.Write(stmt.RangeStart, "Range start must be a number");
return(false);
}
var endType = stmt.RangeEnd.Accept(expressionAnalyzer);
if (endType != "int")
{
ErrorWriter.Write(stmt.RangeEnd, "Range end must be a number");
return(false);
}
var valid = true;
// lock the variable so it can't be modified during the loop
environment.setLock(identifier.Name, true);
foreach (var statement in stmt.Block)
{
valid = statement.Accept(this) && valid;
}
environment.setLock(identifier.Name, false);
return(valid);
}
