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by vram22
2741 days ago
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>You're welcome. Here's another quick example. It may or may not touch on your or the GGGP's point. So, no need to reply. I'll reply anyway, to say thanks again :) I'll admit that I'm a bit phased by P6 phasers :) Had come across them just recently in the docs, initially thought, on a brief look, that at least the ENTER and LEAVE phasers were something like Python's __enter__ and __exit__ special methods used with context managers / "with" statements, or a way of wrapping a function call (or statement) in pre- and post-function invocations. which can be done with decorators in Python. But it seems like phasers may be something more, if not different. Also, there are many other kinds. Need to look into it some, including the "time traveling" code part. |
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.oO ( a pun set to stun? )
> ENTER and LEAVE ... like Python's __enter__ and __exit__
Aiui their primary usage involves similar use-cases and sugar.
The common aspect is that some code is declared and then the language/compiler calls that code when the time is right.
> But it seems like phasers may be something more, if not different.
Aiui P6:
* Has more of these hooks for block processing (eg PRE and POST for convenient pre and post condition assertions);
* Has hooks that aren't for blocks but instead much larger scale phases of program execution (eg there's CHECK which runs at the end of compilation, before running the program).
Also...
> Need to look into it some, including the "time traveling" code part.
What I meant by "time traveling" is as follows.
The compiler calls phased code when the times is right. Some of the time this is implicit. For example, in this Python code the __exit__ code gets called automatically by the Python interpreter as the block is exited:
P6 phases can return values as follows: the first `now` happens during regular run time. But the second happens during CHECK time -- which is at the end of compilation, before the program starts to run. The compiler knows to run the CHECK code earlier, then store the result, then subtract that from the `now` run at normal run-time.I don't recall who first called that time traveling and I'm not even sure on reflection whether it makes sense to call it that but that's what I meant.