On Jan 27, 2:49 pm, "André" <[EMAIL PROTECTED]> wrote: > On Jan 27, 6:19 pm, "Russ P." <[EMAIL PROTECTED]> wrote: > > > > > A while back I came across a tentative proposal from way back in 2000 > > for optional static typing in Python: > > >http://www.python.org/~guido/static-typing > > > Two motivations were given: > > > -- faster code > > -- better compile-time error detection > > > I'd like to suggest a third, which could help extend Python into the > > safety-critical domain: > > > -- facilitates automated source-code analysis > > > There has been much heated debate in the past about whether Python is > > appropriate for safety-critical software. Some argue that, with > > thorough testing, Python code can be as reliable as code in any > > language. Well, maybe. But then, a famous computer scientist once > > remarked that, > > > "Program testing can be used to show the presence of bugs, but never > > to show their absence!" --Edsger Dijkstra > > > The next step beyond extensive testing is automated, "static" analysis > > of source-code ("static" in the sense of analyzing it without actually > > running it). For example, Spark Ada is a subset of Ada with > > programming by contract, and in some cases it can formally prove the > > correctness of a program by static analysis. > > > Then there is Java Pathfinder (http://javapathfinder.sourceforge.net), > > an "explicit state software model checker." The developers of JPF > > wanted > > to use it on a prototype safety-critical application that I wrote in > > Python, but JPF only works on Java code. We considered somehow using > > Jython and Jythonc, but neither did the trick. So they ended up having > > someone manually convert my Python code to Java! (The problem is that > > my code was still in flux, and the Java and Python versions have now > > diverged.) > > > In any case, optional static typing in Python would help tremendously > > here. The hardest part of automated conversion of Python to a > > statically typed language is the problem of type inference. If the > > types are explicitly declared, that problem obviously goes away. > > Explicit typing would also greatly facilitate the development of a > > "Python Pathfinder," so the conversion would perhaps not even be > > necessary in the first place. > > > Note also that, while "static" type checking would be ideal, > > "explicit" typing would be a major step in the right direction and > > would probably be much easier to implement. That is, provide a syntax > > to explicitly declare types, then just check them at run time. A > > relatively simple pre-processor could be implemented to convert the > > explicit type declarations into "isinstance" checks or some such > > thing. (A pre-processor command-line argument could be provided to > > disable the type checks for more efficient production runs if > > desired.) > > > I noticed that Guido has expressed further interest in static typing > > three or four years ago on his blog. Does anyone know the current > > status of this project? Thanks. > > Perhaps this:http://www.python.org/dev/peps/pep-3107/might be > relevant? > André
Thanks. If I read this correctly, this PEP is on track for Python 3.0. Wonderful! -- http://mail.python.org/mailman/listinfo/python-list
