[Python-Dev] A Hygienic Macro System in Python? (original) (raw)

Bernhard Herzog bh@intevation.de
19 Mar 2002 12🔞59 +0100

Greg Ewing <greg@cosc.canterbury.ac.nz> writes:

I've been trying to think of a Pythonic syntax for passing code blocks to procedures. The best thing I've come up with so far is something like

lock.do: something()

Another approach, which I've been thinking about for quite some time now:

under <expr>:
    something()

where evaluates to a controller object that implements a certain interface. The code above would be more or less equivalent to this (the controller variable would only exist in the interpreter somewhere):

__controller__ = <expr>
while __controller__.should_run():
    try:
        try:
            __controller__.start()
            something(x)
            __controller__.end()
        except:
            __controller__.exception()
    finally:
        __controller__.exit()

This sort of thing would make some parts of Sketch a bit easier. I've quite a few places with code like:

doc.BeginTransaction() try: try: something() except: # an error occurred part way through. make sure everything # is reverted (sort of a rollback) doc.AbortTransaction() finally: doc.EndTransaction()

This could be replaced by:

under doc.Transaction():
    something()

Bernhard

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