On Mon, 24 Aug 2009 12:45:25 +1000, Ben Finney wrote: > greg <g...@cosc.canterbury.ac.nz> writes: > >> J. Cliff Dyer wrote: >> >> > What happens if you use a literal like 0x10f 304? >> >> To me the obvious thing to do is concatenate them textually and then >> treat the whole thing as a single numeric literal. Anything else >> wouldn't be sane, IMO.
Agreed. It's the only sane way to deal with concatenating numeric literals. It makes it simple and easy to understand: remove the whitespace from inside the literal, and parse as normal. 123 4567 => 1234567 # legal 0xff 123 => 0xff123 # legal 123 0xff => 1230xff # illegal The first two examples would be legal, the last would raise a syntax error, for obvious reasons. This would also work for floats: 1.23 4e5 => 1.234e5 # legal 1.23 4.5 => 1.234.5 # illegal 1e23 4e5 => 1e234e5 # illegal > Yet, as was pointed out, that behaviour would be inconsistent with the > concatenation of string literals:: > > >>> "abc" r'def' u"ghi" 'jkl' > u'abcdefghijkl' Unicode/byte conversion is obviously a special case, and arguably should have been prohibited, although "practicality beats purity" suggests that a single unicode string in the sequence should make the lot unicode. (What else could it mean?) In any case, numeric concatenation and string concatenation are very different beasts. With strings, you have to interpret each piece as either bytes or characters, you have to treat escapes specially, you have to deal with matching delimiters. For numeric concatenation, none of those complications is relevant: there is no equivalent to the byte/ character dichotomy, there are no escape sequences, there are no delimiters. Numeric literals are much simpler than string literals, consequently the concatenation rule can be correspondingly simpler too. There's no need to complicate it by *adding* complexity: you can't have mixed bases in a single numeric literal without spaces, why would you expect to have mixed bases in one with spaces? -- Steven -- http://mail.python.org/mailman/listinfo/python-list
