private static LNode ChangePath(LNode call, LNode path, IMacroContext context, Func <LNode, IMacroContext, LNode> change)
{
foreach (var index in path.AsList(CodeSymbols.Tuple))
{
// Check if index is an integer, a negated integer, or an
// identifier matching the name of an argument of `call`...
if (index.Value is int iArg ||
index.Calls(S.Sub, 1) && index[0].Value is int negArg && ((iArg = -negArg) & 0) == 0 ||
index.IsId &&
(iArg = EnumerableExt.FirstIndexWhere <LNode>(call, n => n.Name == index.Name) ?? -1) != -1 &&
((iArg += call.Min) & 0) == 0)
{
LNode arg = call.TryGet(iArg, null);
if (arg == null)
{
context.Warning(path, "Index is out of range ({1})", iArg, call.Min <= call.Max
? "expected {0} to {1}".Localized(call.Min, call.Max)
: "'{0}' has no children".Localized(LNode.Printer.Print(call, null, ParsingMode.Expressions)));
}
else
{
call = call.WithChildChanged(iArg, change(arg, context));
}
}
