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Isn't that pretty common? The [] operator acts like find or insert default value, so you can do nice things like ++map[key]. The map.find(key) works if you don'

Isn't that pretty common? The [] operator acts like find or insert default value, so you can do nice things like ++map[key]. The map.find(key) works if you don't want to insert, it will return map.end() if the key couldn't be found.

deredede 4y ago
My only gripe with find() is that you can't do `if (auto it = map.find(key))`. Otherwise yes, that's the way.
- account42 4y ago
  At least you can do `if (auto it = map.find(key); it != map.end())` since C++17.
  - deredede 4y ago
    I didn't know that was possible, thanks. It's worse than in other languages imo but better than the existing C++ alternatives, I will use it.
masklinn 4y ago
> Isn't that pretty common? AFAIK basically just 3 wide-spread languages which do this, and they're all known for their idiosyncratic behaviour: C++, Perl, and PHP. A few languages provide this as opt-in via a subtype (Python's defaultdict) or init (Ruby's Hash.new with a block parameter). Some more will do it via an opt-in callsite API e.g. Python's `setdefault`, Java's `computeIfAbsent`, Rust's `entry` API.
- kragen 4y ago
  perl only does this in some cases; unlike with std::map, this is safe: my $x = $h{$v}; this is not safe because it autovivifies $h{$v} as an ARRAY ref: my $x = $h{$v}[$i]; with respect to idiosyncratic behavior, if a language doesn't have idiosyncratic behavior, it has no reason to exist; it's just gratuitously incompatible syntax for already-available semantics