How to trace?

[Skip Montanaro]

I downloaded and tried MacroPy today, with the thought that I would initially use it to trace execution of some code I was having trouble with. This is the first example shown on the PyPI page:

with trace:
    sum([x + 5 for x in range(3)])

Not knowing any better, I tried this at the Python prompt:

import macropy.tracing
with trace:
 sum([x + 5 for x in range(3)])

This, unfortunately fails:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: __exit__

Reading elsewhere later, I discovered that I was missing some other initialization, but I'm not entirely sure what that is. Assume I want to simply trace the body of a single function:

def f(a, b):
    return a*5 + b / 7.0

If I don't want to disturb any other code, what do I need to do beyond this transformation?

def f(a, b):
    from macropy.tracing import trace:
    with trace:
        return a*5 + b / 7.0

In fact, looking at the tracing examples in the doc: https://github.com/lihaoyi/macropy#tracing (fourth example, "Lastly, trace can be used as a block macro") it appears I've done what I'm supposed to do. But clearly that is not enough. Shouldn't there be a "hello world" example which is complete in its entirety on PyPI or as part of the documentation?

Thanks,

Skip

[Haoyi Li]

MacroPy needs to be bootstrapped *before* you load any file that uses macros. There is a complete example here, kinda tricky but unavoidable given the restrictions of how macropy works (i.e. at runtime, no pre-processing). Go try it ^_^

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