2011/3/11 Stefan Behnel <stefan...@behnel.de>: > Hi, > > ticket 654 describes a code generation problem where the arguments to a cdef > function are not being evaluated in the order they are written down in the > code. > > http://trac.cython.org/cython_trac/ticket/654 > > This introduces problems when the arguments have side effects or are not > simple, e.g. they are function calls themselves or are taken from object > attributes or live in a closure. For example, > > f(g(a), a.x, h(a)) > > will produce different results depending on the evaluation order if g or h > change the value of a.x. > > However, apparently, the order of evaluation is only guaranteed by Python, > not by C. Now, the question is: what are the right semantics for Cython > here: follow Python or C? >
+1 for Python, Cython is mostly Python than C, btw I don't think that it makes much sense. > Personally, I think it would be nice to keep up Python's semantics, but when > I implemented this I broke quite some code in Sage (you may have noticed > that the sage-build project in Hudson has been red for a while). There are > things in C and especially in C++ that cannot be easily copied into a > temporary variable in order to make sure they are evaluated before the > following arguments. This is not a problem for Python function calls where > all arguments end up being copied (and often converted) anyway. It is a > problem for C function calls, though. > > What do you think about this? > > f(g(a), a.x, h(a)) Why could not this be translated into: tmp1 = g(a) tmp2 = a.x tmp3 = h(a) f(tmp1, tmp2, tmp3) -- vitja. _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
