######################################################################
    Cache::Historical 0.02
######################################################################

NAME
    Cache::Historical - Cache historical values

SYNOPSIS
        use Cache::Historical;

        my $cache = Cache::Historical->new();
 
           # Set a key's value on a specific date
        $cache->set( $dt, $key, $value );

           # Get a key's value on a specific date
        my $value = $cache->get( $dt, $key ); 

           # Same as 'get', but if we don't have a value at $dt, but we 
           # do have values for dates < $dt, return the previous 
           # historic value. 
        $cache->get_interpolated( $dt, $key );

DESCRIPTION
    Cache::Historical caches historical values by key and date. If you have
    something like historical stock quotes, for example

        2008-01-02 msft 35.22
        2008-01-03 msft 35.37
        2008-01-04 msft 34.38
        2008-01-07 msft 34.61

    then you can store them in Cache::Historical like

        my $cache = Cache::Historical->new();

        my $fmt = DateTime::Format::Strptime->new(
                      pattern => "%Y-%m-%d");

        $cache->set( $fmt->parse_datetime("2008-01-02"), "msft", 35.22 );
        $cache->set( $fmt->parse_datetime("2008-01-03"), "msft", 35.37 );
        $cache->set( $fmt->parse_datetime("2008-01-04"), "msft", 34.38 );
        $cache->set( $fmt->parse_datetime("2008-01-07"), "msft", 34.61 );

    and retrieve them later by date:

        my $dt = $fmt->parse_datetime("2008-01-03");

          # Returns 35.37
        my $value = $cache->get( $dt, "msft" );

    Even if there's no value available for a given date, but there are
    historical values that predate the requested date, "get_interpolated()"
    will return the next best historical value:

        my $dt = $fmt->parse_datetime("2008-01-06");

          # Returns undef, no value available for 2008-01-06
        my $value = $cache->get( $dt, "msft" );

          # Returns 34.48, the value for 2008-01-04, instead.
        $value = $cache->get_interpolated( $dt, "msft" );

  Additional methods
    keys
               # List all keys
            my @keys = $cache->keys();

    time_range
               # List the time range for which we have values for $key
            my($from, $to) = $cache->time_range( $key );

    values
               # List all the values we have for $key, sorted by date
               # ([$dt, $value], [$dt, $value], ...)
            my @results = $cache->values( $key );

    clear
               # Remove all values for a specific key
            $cache->clear( $key );

               # Clear the entire cache
            $cache->clear();

    last_update
               # Return a DateTime object of the last update of a given key
            my $when = $cache->last_update( $key );

    since_last_update
               # Return a DateTime::Duration object since the time of the last
               # update of a given key.
            my $since = $cache->since_last_update( $key );

LEGALESE
        Copyright 2007 by Mike Schilli, all rights reserved. This program is
        free software, you can redistribute it and/or modify it under the
        same terms as Perl itself.

AUTHOR
        2007, Mike Schilli <cpan@perlmeister.com>

