[ID 20000418.004] Uninformative pseudo-hash error message

This is a bug report for perl from ben_tilly@trepp.com,
generated with the help of perlbug 1.26 running under perl 5.00503.


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[Please enter your report here]

One major debugging problem I am running into.  When you try to
access a non-existent key in a pseudo-hash it gives you an error
like, "No such array field ..."

It would be a *massive* improvement if the error could state
which field it was complaining about!  It is very easy for that
to not be obvious if you are using an array slice, in a loop,
the access is on the first line after an if test (particularly
if it is on the branch you are not accessing)...

I was just in the last situation for some time staring at the
wrong branch. :-(

A random note while I am thinking about hashes.  In finance
people use a lot of identifiers that don't hash well.  For
instance trustees may identify loans with loanIDs that are
a mix of mostly numerical data with occasional letters.
Financial securities are labelled by "cusip" which is a
string value produced by rules that defeat easy hashing.
etc.  It would be extremely nice if Perl's hashing performance
was able to degrade gracefully on these data-sets.  Is there
any chance that this would happen?

An example of how you might do it would be to modify Perl's hashes to
have each bucket hold a linked list, but once the length of the linked
list reaches 4, instead of entering another node in a linked list
create a top node in a balanced binary tree.  This would have no
performance penalty when the hashing algorithm was working well, but
if it failed for a particular dataset you would still get an acceptable
performance.

Thanks,
Ben

[Please do not change anything below this line]
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Site configuration information for perl 5.00503:

Configured by torin at Wed Sep 22 00:18:38 PDT 1999.

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration:
  Platform:
    osname=linux, osvers=2.0.36, archname=i386-linux
    uname='linux perv 2.0.36 #2 wed nov 18 03:00:48 pst 1998 i686 unknown '
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef useperlio=undef d_sfio=undef
  Compiler:
    cc='cc', optimize='-O2', gccversion=2.95.1 19990809 (prerelease)
    cppflags='-Dbool=char -DHAS_BOOL -D_REENTRANT -DDEBIAN -I/usr/local/include'
    ccflags ='-Dbool=char -DHAS_BOOL -D_REENTRANT -DDEBIAN -I/usr/local/include'
    stdchar='char', d_stdstdio=undef, usevfork=false
    intsize=4, longsize=4, ptrsize=4, doublesize=8
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lndbm -lgdbm -ldbm -ldb -ldl -lm -lc -lposix -lcrypt
    libc=, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    

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@INC for perl 5.00503:
    /usr/lib/perl5/5.005/i386-linux
    /usr/lib/perl5/5.005
    /usr/local/lib/site_perl/i386-linux
    /usr/local/lib/site_perl
    /usr/lib/perl5
    .

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Environment for perl 5.00503:
    HOME=/home/tilly
    LANG=C
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games
    PERL_BADLANG (unset)
    SHELL=/bin/bash

• [ID 20000418.004] Uninformative pseudo-hash error message by Benjamin J. Tilly