public override Expression CreateExpression(VisualProgram context)
{
// If a start value is provided, set the target variable to that value. If not provided, do not
var init = Start.HasValue
? Variable.ResolveRequiredSetterExpression(context, Start.ResolveRequiredExpression(context))
: Expression.Empty();
// Store some re-used expressions to prevent re-resolving them
var variableExpr = Variable.ResolveRequiredGetterExpression(context);
var changeExpr = Change.ResolveExpression(context) ?? Expression.Constant(1d, typeof(double));
var endExpr = End.ResolveRequiredExpression(context);
var loop = LoopFactory.CreateLoop(
// Loop body
Expression.Block(
// Run the given body
Body.ResolveStatement(context),
// Update the variable by 'Change' amount
Variable.ResolveRequiredSetterExpression(
context,
Expression.Add(variableExpr, changeExpr)
)
),
// Loop condition
Expression.Condition(
// If the 'Change' value is >= 0...
Expression.GreaterThanOrEqual(
changeExpr,
Expression.Constant(0d, typeof(double))
),
// Then the condition is whether the variable is less than or equal to the end
Expression.LessThanOrEqual(variableExpr, endExpr),
// Otherwise (if 'Change' is < 0) the condition is whether variable is greater than or equal to the end
Expression.GreaterThanOrEqual(variableExpr, endExpr)
)
);
// Return a block that sets the initial value then executes the loop
return(Expression.Block(init, loop));
}
public override Expression CreateExpression(VisualProgram context) => LoopFactory.CreateLoop(
Body.ResolveStatement(context),
Condition.ResolveRequiredExpression(context)
);