disallow line-terminating colons

[andrewcooke]

About 1 time in 5, when I run

julia runtests.jl

in the src directory of https://github.com/andrewcooke/Stupid.jl/tree/range-bug I see

: julia runtests.jl 
Prefix
   0 010204 1/02 2/04 1/02
ERROR: Range: length must be non-negative
 in Range1 at range.jl:27
at /home/andrew/.julia/Stupid/src/runtests.jl:4

I have reduced the project as much as (quickly) possible, deleting routines and modules that are not used. But it's still a non-trivial amount of code (it's the analysis of a stream cipher).

I also updated to the latest version of Julia (from git), and still see the problem - I am using Version 0.2.0-rc2+105; Commit 5167476 2013-10-31 18:03:04 UTC; x86_64-suse-linux

Feel free to ask questions; I have no idea how to debug something like this - the stack trace shown seems to be completely wrong (it's missing tests() and test_distance() - you can see some output generated by test_distance() before the ERROR).

(I think it's a bug in Julia because although I was using random numbers elsewhere, that test, which is all that is left in the branch, where the code still fails, is deterministic. Yet the error is intermittent and the stack trace seems incorrect).

Cheers, Andrew

[JeffBezanson]

This is because of the pythonic colon at the end of Prefix.jl:21, which is getting parsed across the line break as h1:consume(t). This certainly makes me think allowing colons to parse across lines is a bad thing.

The second argument to colon is a large integer hash value, which is sometimes outside the range of the Int type, leading to the error. We only give the error in one direction, but there should probably be a different error for too-large ranges.

[andrewcooke]

Oh, I feel like an idiot. I really appreciate all the help here and on the list. Sorry for posting this and wasting your time. Thanks!

[JeffBezanson]

I think this issue raises a very valid point: programmers are likely to try : at the end of a line, and instead of getting an error you just get highly unexpected behavior. I think this should be fixed.

[StefanKarpinski]

Not at all. I think the actionable result of this issue is that we shouldn't allow colon syntax to be split across lines. There's no reasonable reason to do that and it's very likely that many Pythonistas will make the same mistake in the future.

[pao]

Reopened with updated title.