27 March, 2010

stack trace in perl

As a user, I hate java stack traces (because they expose the guts of the program, when I don't care about those guts). But as a programmer, I have come to realise how much I like them, when faced with errors like this:

Can't call method "emitCode" on an undefined value at /Users/benc/src/stupid/stupid-crypto/src/Stupid/C.pm line 27.

where the error is actually deep inside the call on line 27.

So googling around I found this line to put at the start of a program:

$SIG{ __DIE__ } = sub { Carp::confess( @_ ) };

which replaces those short die messages with a stack dump produced by Carp:

Can't call method "emitCode" on an undefined value at /Users/benc/src/stupid/stupid-crypto/src/Stupid/C.pm line 27.
at /Users/benc/src/stupid/stupid-crypto/src/Stupid/C.pm line 7
Stupid::C::__ANON__('Can\'t call method "emitCode" on an undefined value at /Users...') called at /Users/benc/src/stupid/stupid-crypto/src/Stupid/C.pm line 27
Stupid::LanguageWrapper::emitCode('Stupid::LanguageWrapper=HASH(0x8ff9b4)') called at ../src/stupid.pl line 44

which I hope I'll find more useful...

20 March, 2010

so many ways to hash

I was making commandline tools for stupid to drive the example sha256 code, resulting in multiple tools that deliberately did the same but using different language backends. Then I realised I have a shitload of (where shitload==4) md5sum commandline tools already:

$ echo abc | md5

$ echo abc | gmd5sum
0bee89b07a248e27c83fc3d5951213c1  -

$ echo abc | openssl dgst 

$ echo abc | gpg2 --print-md md5
0B EE 89 B0 7A 24 8E 27  C8 3F C3 D5 95 12 13 C1

13 March, 2010


You(*) whisper to X, "the same package [GNU coreutils] which provides seq"
You(*) whisper to X, "the command line utility"
You(*) whisper to X, "also provides factor"
You(*) whisper to X, "which outputs prime factors"
You(*) whisper to X, "makes me want to start making fucked up shell scripts"
You(*) whisper to X, "that use goedel numbering"
You(*) whisper to X, "for some purpose."
You(*) whisper to X, "i have to wonder how a commandline utility for factoring primes is 'core' in any way, though"

06 March, 2010

ASCII art C++ constants

I came across Multi-Dimensional Analog Literals in C++. This is an implementation in standard C++ templates that lets you write constants out using ASCII art (in 1, 2 or 3 dimensions):

unsigned int c = ( o-----o
| !
! !
! !
o-----o ).area;

assert( c == (I-----I) * (I-------I) );

I think the same would be straightforward to implement using Template Haskell's quasiquoting mechanism, which allows you to embed parsers for fairly arbitrary sublanguages inside Haskell source. I wonder what other languages you could also implement something like this in.