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.\" ========================================================================
.\"
.IX Title "Historical 3pm"
.TH Historical 3pm "2018-06-21" "perl v5.26.2" "User Contributed Perl Documentation"
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.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Cache::Historical \- Cache historical values
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use Cache::Historical;
\&
\&    my $cache = Cache::Historical\->new();
\& 
\&       # Set a key\*(Aqs value on a specific date
\&    $cache\->set( $dt, $key, $value );
\&
\&       # Get a key\*(Aqs value on a specific date
\&    my $value = $cache\->get( $dt, $key ); 
\&
\&       # Same as \*(Aqget\*(Aq, but if we don\*(Aqt have a value at $dt, but we 
\&       # do have values for dates < $dt, return the previous 
\&       # historic value. 
\&    $cache\->get_interpolated( $dt, $key );
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Cache::Historical caches historical values by key and date. If you have
something like historical stock quotes, for example
.PP
.Vb 4
\&    2008\-01\-02 msft 35.22
\&    2008\-01\-03 msft 35.37
\&    2008\-01\-04 msft 34.38
\&    2008\-01\-07 msft 34.61
.Ve
.PP
then you can store them in Cache::Historical like
.PP
.Vb 1
\&    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 );
.Ve
.PP
and retrieve them later by date:
.PP
.Vb 1
\&    my $dt = $fmt\->parse_datetime("2008\-01\-03");
\&
\&      # Returns 35.37
\&    my $value = $cache\->get( $dt, "msft" );
.Ve
.PP
Even if there's no value available for a given date, but there are historical 
values that predate the requested date, \f(CW\*(C`get_interpolated()\*(C'\fR will return
the next best historical value:
.PP
.Vb 1
\&    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" );
.Ve
.SS "Methods"
.IX Subsection "Methods"
.IP "\fInew()\fR" 4
.IX Item "new()"
Creates the object. Takes the SQLite file to put the date into as
an additional parameter:
.Sp
.Vb 3
\&    my $cache = Cache::Historical\->new(
\&        sqlite_file => "/tmp/mydata.dat",
\&    );
.Ve
.Sp
The SQLite file defaults to
.Sp
.Vb 1
\&    $HOME/.cache\-historical/cache\-historical.dat
.Ve
.Sp
so if you have multiple caches, you need to use different
SQLite files.
.IP "\fItime_range()\fR" 4
.IX Item "time_range()"
.Vb 2
\&       # List the time range for which we have values for $key
\&    my($from, $to) = $cache\->time_range( $key );
.Ve
.IP "\fIkeys()\fR" 4
.IX Item "keys()"
.Vb 2
\&       # List all keys
\&    my @keys = $cache\->keys();
.Ve
.IP "\fIvalues()\fR" 4
.IX Item "values()"
.Vb 3
\&       # List all the values we have for $key, sorted by date
\&       # ([$dt, $value], [$dt, $value], ...)
\&    my @results = $cache\->values( $key );
.Ve
.IP "\fIclear()\fR" 4
.IX Item "clear()"
.Vb 2
\&       # Remove all values for a specific key
\&    $cache\->clear( $key );
\&
\&       # Clear the entire cache
\&    $cache\->clear();
.Ve
.IP "\fIlast_update()\fR" 4
.IX Item "last_update()"
.Vb 2
\&       # Return a DateTime object of the last update of a given key
\&    my $when = $cache\->last_update( $key );
.Ve
.IP "\fIsince_last_update()\fR" 4
.IX Item "since_last_update()"
.Vb 3
\&       # Return a DateTime::Duration object since the time of the last
\&       # update of a given key.
\&    my $since = $cache\->since_last_update( $key );
.Ve
.SH "LEGALESE"
.IX Header "LEGALESE"
Copyright 2007\-2011 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.
.SH "AUTHOR"
.IX Header "AUTHOR"
2007, Mike Schilli <cpan@perlmeister.com>