On Thu, Nov 6, 2014 at 1:07 PM, Nils Bruin <nbr...@sfu.ca> wrote: > On Thursday, November 6, 2014 10:57:23 AM UTC-8, Robert Bradshaw wrote: >> >> cdef float -> float F >> cdef (float -> float, float, float) -> float G >> cdef (char*) -> (float -> float, float, float) -> float H > > Is there any precedent for an infix operator in type declarations? I find it > really surprising.
The "input -> output" syntax is used for anonymous functions and callable types in several languages, from Haskell to OCaml to Java. Python 3 introduces -> to annotate function return types in PEP 3107. > It's a little better with parentheses I think: > > cdef (float -> float) F > > Without them, the "float F" seems to visually bind much more closely than > the "float -> float", contrary to your proposed precedence. Yeah, the parentheses make this more clear, though cdef float -> (float F) doesn't really have a reasonable interpretation. The syntax "[type] [space] [name]" is a bit unfortunate--we already have ugly, special logic to handle things like "cdef unsigned short int foo" or even worse "def foo(self, int): ..." > Also, C's > convention that "a->b == *a.b" makes the "->" use here unexpected, > especially because it's used in an environment where pointer (type)s are > involved. Yeah, Stefan pointed this out too, though we don't use -> in Cython (except for function return annotation). I think the fact that these are function *pointers* wouldn't need to be called out, given that functions can be assigned to function pointers and function pointers are callable just like functions. They'd behave more like first class function objects. >> cdef lambda float: float F >> cdef lambda (lambda float: float), float, float: float G >> cdef lambda (char*): lambda: (lambda float: float), float, float: >> float H > > > At least this overcomes the infix issue a bit: right from the start, the > "lambda" hints that this is a function type. However, visually again this > reads to me (because : in normal writing a : would separate sentences of > words separated by spaces, hence indicating that a space has higher > precedence than a colon) as: > > cdef lambda float: (float F) > > which can be circumvented by parentheses: > > cdef (lambda float: float) F > > The "lambda" solution doesn't look very appealing here, but I think (with > parentheses) it is the one that is most likely to be unambiguously clear. Yeah, it looks funny, but is harder to miss-interpret. - Robert -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
