Promises show a good use case. It's common to have many promise-laden bits of code and it's clear that the first callback is success, second, error, and third progress.
Having to do "def promise1_success" ... "def promise1_error" ... etc all the way up through 5 promises is a pain.
For event-emitter like things, it's also great to have anonymous functions.
For example, in nodejs, you might have reader.on('data', function(chunk) {}); .... You gain no further insight into what that function does if you have "def handle_reader_data" and then use it once there. There are many cases where you don't need the function name for clarify, and it just clutters the current scope to have it not be anonymous.
Code is also easier to follow if functions like that, used once only as a callback, are immediately defined where they are used, not lines above. When reading code that has a named function above, I'd have to skim the function the first time, see it used, and then trace back through it above knowing what was calling it.
Having to do "def promise1_success" ... "def promise1_error" ... etc all the way up through 5 promises is a pain.
For event-emitter like things, it's also great to have anonymous functions.
For example, in nodejs, you might have reader.on('data', function(chunk) {}); .... You gain no further insight into what that function does if you have "def handle_reader_data" and then use it once there. There are many cases where you don't need the function name for clarify, and it just clutters the current scope to have it not be anonymous.
Code is also easier to follow if functions like that, used once only as a callback, are immediately defined where they are used, not lines above. When reading code that has a named function above, I'd have to skim the function the first time, see it used, and then trace back through it above knowing what was calling it.