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The ! convention is ok but I don't think it's optimal because, in the presence of higher-order functions and related concepts, it's often not clear if a functio

The ! convention is ok but I don't think it's optimal because, in the presence of higher-order functions and related concepts, it's often not clear if a function should be marked as !. For example if I have a map function that applies a function f to a sequence, should I call it map! because I might pass in a function f that mutates the input? If so then it seems like any function that takes a function as input, or any function that might call a method on an object, should get marked with ! just in case. But if I don't mark it that way then the ! marking is not as informative: I might end up with a line consisting only of non-! functions which still mutates the input.

zarzavat 5y ago
map! would mean a function that performs a map in-place on the array by replacing the values. So it would depend on if the callback was encouraged to mutate the array or discouraged from doing so.
- djur 5y ago
  Array#map! actually exists in Ruby, too. It mutates the array item by item. Enumerable#each doesn't have a bang, because it doesn't change the enumerable itself, even though it can mutate the objects contained in the enumerable. This is overall consistent -- there's a distinction between mutating the receiving object and mutating objects contained in or referred to by the receiving object.
dragonwriter 5y ago
Note that “!” in Ruby doesn’t conventionally mean “modifies the receiver”, it means “does something that is similar but less likely to be safe than a method with the same name without ‘!’”. A very common case of this is mutating versions of non-mutating methods, but (1) mutating methods (in stdlib or other idiomatic code bases) that have no non-mutating equivalent are not named with a “!”, and (2) methods are sometimes named with “!” because they do dangerous things compared to a base method that are not mutating the receiver.

zarzavat 5y ago

map! would mean a function that performs a map in-place on the array by replacing the values. So it would depend on if the callback was encouraged to mutate the array or discouraged from doing so.

djur 5y ago
Array#map! actually exists in Ruby, too. It mutates the array item by item. Enumerable#each doesn't have a bang, because it doesn't change the enumerable itself, even though it can mutate the objects contained in the enumerable. This is overall consistent -- there's a distinction between mutating the receiving object and mutating objects contained in or referred to by the receiving object.

dragonwriter 5y ago

Note that “!” in Ruby doesn’t conventionally mean “modifies the receiver”, it means “does something that is similar but less likely to be safe than a method with the same name without ‘!’”. A very common case of this is mutating versions of non-mutating methods, but (1) mutating methods (in stdlib or other idiomatic code bases) that have no non-mutating equivalent are not named with a “!”, and (2) methods are sometimes named with “!” because they do dangerous things compared to a base method that are not mutating the receiver.