On Monday, March 3, 2014 7:30:17 PM UTC+5:30, Chris Angelico wrote: > On Tue, Mar 4, 2014 at 12:48 AM, Rustom Mody wrote: > > ? [1,2] + [[3,4],[5]] > > ERROR: Type error in application > > *** expression : [1,2] + [[3,4],[5]] > > *** term : [1,2] > > *** type : [Int] > > *** does not match : [[Int]] > > IOW [1,2,[3,4],[5]] > > is a type-wise ill-formed expression just as in python > > [[1,2]) > > is syntax-wise ill-formed > > Is it worth having such a restriction? > > Thats a different argument...
> How do you know that [1,2] is a list that must contain nothing but > integers? By extension, it's also a list that must contain positive > integers less than three, so adding [5] violates that. And [] is a > list that must contain nothing, ergo it can't be added to, although > (since it contains nothing) it can be added to anything. If 'integer-less-than-3' were a type then yes there would be this problem. More generally, if types could overlap then automatic type-inference is impossible Whether all thats good is as I earlier said a different argument The OP asked about FP and so its appropriate to mention how python's and standard FPL's choices differ -- https://mail.python.org/mailman/listinfo/python-list
