Hacker News Reader

Comment by jnoller | Hacker News Reader

Actually, Python generators will be changing quite a bit soon: http://www.python.org/dev/peps/pep-0380/

Thanks for the link, I had not read 0380.

The proposed solution seems to be increasing syntactic complexity rather than reducing it by adding another keyword, "from" into the mix which is hardly optimal imo.

This to me indicates a systematic logical flaw of thinking of hitting a "yield" in the call stack as analagous to "return". When in fact it is the inverse and analagous to waiting for a function to return and thus more similar to a print() function call. The whole point of coroutine yielding is that it inverts the point of view of a call stack and allows the called routine to be the calling routine as well.

I still use Python for some things and have too many fond memories to ever hate it, but even if generators get cleaned up I'll probably stay w/ Lua for pipeline type projects as I've grown too used to runtime within an order of magnitude of C, better coroutines, and its more Scheme-like nature.

My interpretation of the "yield" keyword is not that of a coroutine yield, but that of "cough up the following value", which is more in line with "return". Under that interpretation, the fact that generators can also be used to implement coroutines is a coincidence with unfortunate terminology namespace conflicts.

I looked around a bit for the original semantic intention behind choosing "yield" as a keyword, but came up empty. Anyone?

It is my understanding "yield" refers to "execution control". If semantic meaning is of concern over lexical, let us ignore the names "coroutine" and "generator" and focus on the general logic of code continuation. That is, the difference between pausing the current execution context vs destroying it.

Function call: halt further processing of current call stack, execute procedures, resume call stack after function call when control returns.

Yield: halt further processing of current call stack, execute procedures, resume call stack after yield when control returns.

Return: destroy current call stack.

The variation present on the code continuation axis is far more significant than the variation on the coughing-up-values axis.

I think, in this case, 'yield' is being used less in the sense of a street sign, and more in the sense of crop yield.

Reply on news.ycombinator.com