To complete Philippe's answer : As Bird and Wadler continue :
"The major consequence of the discipline imposed by strong-typing is that any expression which cannot be assigned a "sensible" type is regarded as not being well-formed and is rejected by the computer before evaluation. Such expression have _no_ value: they are simply regarded as illegal." But Skip, I am sure that you can easily find an example by yourself. For example, replace "+" by a function that does different things depending on its argument type. Francis Girard Le mercredi 2 Février 2005 10:27, Philippe Fremy a écrit : > Skip Montanaro wrote: > > Francis> "Every well-formed expression of the language can be > > assigned a Francis> type that can be deduced from the constituents of the > > Francis> expression alone." Bird and Wadler, Introduction to Functional > > Francis> Programming, 1988 > > > > Francis> This is certainly not the case for Python since one and the > > Francis> same variable can have different types depending upon the > > Francis> execution context. Example : > > > > Francis> 1- if a is None: > > Francis> 2- b = 1 > > Francis> 3- else: > > Francis> 4- b = "Phew" > > Francis> 5- b = b + 1 > > > > Francis> One cannot statically determine the type of b by examining > > the Francis> line 5- alone. > > > > Do you have an example using a correct code fragment? It makes no sense > > to infer types in code that would clearly raise runtime errors: > > On the contrary, the point of type inference is to detect such errors. > If the program was always well-formed, there would be no point in > developing a type inference tool. > > Philippe -- http://mail.python.org/mailman/listinfo/python-list
