Andres Freund <and...@anarazel.de> writes: > Unfortunately foreach(ListCell *lc, ...) doesn't work with the current > definition. Which I think isn't great, because the large scopes for loop > iteration variables imo makes the code harder to reason about.
Yeah, I tried to make that possible when I redid those macros, but couldn't find a way :-(. Even granting that we're willing to have a different macro for this use-case, it doesn't seem easy, because you can only put one <declaration> into the first element of a for (;;). That makes the other idea (of a foreach-ish macro declaring the listcell value variable) problematic, too :-(. One idea is that we could do something like foreach_variant(identifier, list_value) { type *v = (type *) lfirst_variant(identifier); ... } where the "identifier" isn't actually a variable name but just something we use to construct the ForEachState variable's name. (The only reason we need it is to avoid confusion in cases with nested foreach's.) The lfirst_variant macro would fetch the correct value just by looking at the ForEachState, so there's no separate ListCell* variable at all. regards, tom lane