Sorry for the repeat, but the upload server removed newlines from my
description, rendering it practically unreadable. Here is the more
readable form:
theo
# this is a hash that also acts like a funny array. It preserves order
# like an array(akin to Tie::IxHash), but also has some other specific
# behavior that is described below ( the `===' I am using here to mean
# `equivalent to')
# where $x is an integer $x >= 0
# then $h{$x} === $h{$h{"-$x"}}
#
# here is a sample hash:
# $th = tie %h, __PACKAGE__
# %h = qw( _foo bar
# _baz fup
# );
# Taowebs::Tie::Silk; these are the behaviors we are after:
# 1) when accessed with a negative number it returns the hash hey for
# the indicated pair(need to be careful with a `minus zero' key
# MUST be a string because perl compiler will convert an unquoted -0 to 0)
# $h{'-0'} === _foo
# $h{-1} === _baz
# 2) when accessed with a positive integer it returns the value for
# the associated key pair (same as fetching it with the normal
# hash key, but now we are accessing it with pseudo-array indexing
# using {} instead of [] notation)
# $h{0} === bar === $h{_foo} === $h{$h{'-0'}}
# $h{1} === fup === $h{_baz} === $h{$h{-1}}
# $h{_baz} === fup
# $h{_foo} === bar
# 3) a normal hash key preceded by a `-' (minus sign) returns the
# index of that pair ( except when setting a value this way, see #4)
# $h{-_baz} === 1
# $h{-_foo} === 0
# 4) when setting an element and preceding the hash key with a minus
# sign `-' this actually replaces the hash key with the value
# therefore we have:
# $h{-_foo} = '_new_foo' === $h{'-0'}
# $h{_new_foo} === bar
# $h{-_new_foo} === 0
# $h{'-0'} === _new_foo
# 5) you cannot set a new slot with an integer unless the integer
# matches the next open slot, otherwise confusion may ensue
#
Perl Authors Upload Server writes:
>
> The following module was proposed for inclusion in the Module List:
>
> modid: Tie::Silk
> DSLIP: bdprp
> description: Indexed hash prepend w/ `-' to get index/key
> userid: DIRT (Theo Lengyel)
> chapterid: 6 (Data_Type_Utilities)
> communities:
>
> similar:
> Tie::IxHash
>
> rationale:
>
> Tie::Silk - Silk = Somewhat Intuitive List Knitter
>
> This is an indexed hash with some added strange behavior. It is
> useful for keeping track of several related lists based on the same
> key set. When an (existing) key is prepended with a `-' (minus sign
> - regular keys may NOT begin with a `-') it returns the index for
> that element. When an index (integer) is used to access the hash it
> acts like an array (new values may NOT be introduced with integer
> keys) and returns/sets the VALUE in that slot. When an integer is
> prepended with a `-' it returns/sets the corresponding KEY for that
> slot. When accessed with normal text keys is behaves like a normal
> hash, except that order is preserved.
>
> # this is a hash that also acts like a funny array. It preserves
> order # like an array(akin to Tie::IxHash), but also has some other
> specific # behavior that is described below ( the `===' I am using
> here to mean # `equivalent to') # where $x is an integer $x >= 0 #
> then $h{$x} === $h{$h{"-$x"}} # # here is a sample hash: # $th = tie
> %h, __PACKAGE__ # %h = qw( _foo bar # _baz fup # ); #
> Taowebs::Tie::Silk; these are the behaviors we are after: # 1) when
> accessed with a negative number it returns the hash hey for # the
> indicated pair(need to be careful with a `minus zero' key # MUST be
> a string because perl compiler will convert an unquoted -0 to 0) #
> $h{'-0'} === _foo # $h{-1} === _baz # 2) when accessed with a
> positive integer it returns the value for # the associated key pair
> (same as fetching it with the normal # hash key, but now we are
> accessing it with pseudo-array indexing # using {} instead of []
> notation) # $h{0} === bar === $h{_foo} === $h{$h{'-0'}} # $h{1} ===
> fup === $h{_baz} === $h{$h{-1}} # $h{_baz} === fup # $h{_foo} ===
> bar # 3) a normal hash key preceded by a `-' (minus sign) returns
> the # index of that pair ( except when setting a value this way, see
> #4) # $h{-_baz} === 1 # $h{-_foo} === 0 # 4) when setting an element
> and preceding the hash key with a minus # sign `-' this actually
> replaces the hash key with the value # therefore we have: #
> $h{-_foo} = '_new_foo' === $h{'-0'} # equivalently: # $h{'-0'} =
> '_new_foo' === $h{'-0'} # $h{_new_foo} === bar # $h{-_new_foo} === 0
> # $h{'-0'} === _new_foo # 5) you cannot set a new slot with an
> integer unless the integer matches the next open slot, otherwise
> confusion may ensue #
>
> enteredby: DIRT (Theo Lengyel)
> enteredon: Thu Nov 6 19:38:15 2003 GMT
>
> The resulting entry would be:
>
> Tie::
> ::Silk bdprp Indexed hash prepend w/ `-' to get index/key DIRT
>
>
> Thanks for registering,
> --
> The PAUSE
>
> PS: The following links are only valid for module list maintainers:
>
> Registration form with editing capabilities:
>
> https://pause.perl.org/pause/authenquery?ACTION=add_mod&USERID=73500000_95e73362a06ea6fb&SUBMIT_pause99_add_mod_preview=1
> Immediate (one click) registration:
>
> https://pause.perl.org/pause/authenquery?ACTION=add_mod&USERID=73500000_95e73362a06ea6fb&SUBMIT_pause99_add_mod_insertit=1
