tame/core/vector/length.xml

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<?xml version="1.0"?>
<!--
Copyright (C) 2017 R-T Specialty, LLC.
This file is part of tame-core.
tame-core is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
-->
<package xmlns="http://www.lovullo.com/rater"
xmlns:c="http://www.lovullo.com/calc"
xmlns:t="http://www.lovullo.com/rater/apply-template"
core="true"
desc="Operations Based on Vector Length">
<import package="../base" />
<import package="../numeric/common" export="true" />
See the respective test specification for examples.
<section title="Non-empty Vectors">
\ref{_first-nonempty_} will yield the result of the first toplevel
expression that is not an empty vector.
This template yields an empty vector if no non-empty vectors are found.
<template name="_first-nonempty_"
desc="Return the first non-empty vector">
<param name="@values@" desc="List of vectors" />
<c:let>
<c:values>
<!-- avoid having to copy @values@ multiple times -->
<c:value name="_list" type="float"
desc="Result of body expression">
<c:set>
<param-copy name="@values@" />
</c:set>
</c:value>
</c:values>
<c:apply name="_first_nonempty">
<c:arg name="list">
<c:value-of name="_list" />
</c:arg>
<c:arg name="index">
<c:const value="0" desc="First element" />
</c:arg>
<c:arg name="length">
<c:length-of>
<c:value-of name="_list" />
</c:length-of>
</c:arg>
</c:apply>
</c:let>
</template>
Its helper function is \ref{_first_nonempty},
which recurses through each vector element until a non-empty vector is
encountered.
<function name="_first_nonempty"
desc="Return the first non-empty vector">
<param name="list" type="float" set="vector"
desc="List of vectors to process" />
<param name="index" type="integer"
desc="Current index (for recursion), decrementing" />
<param name="length" type="integer"
desc="Length of list" />
<c:let>
<c:values>
<c:value name="cur_len" type="integer"
desc="Length of current vector">
<c:length-of>
<c:value-of name="list" index="index" />
</c:length-of>
</c:value>
</c:values>
<c:cases>
<!-- if none were found (end of list), return empty vector -->
<c:case>
<c:when name="index">
<c:gte>
<c:value-of name="length" />
</c:gte>
</c:when>
<c:set />
</c:case>
<!-- non-empty vector, return it -->
<c:case>
<c:when name="cur_len">
<c:gt>
<c:const value="0" desc="Vector length" />
</c:gt>
</c:when>
<c:value-of name="list" index="index" />
</c:case>
<!-- vector was empty, keep going (decrement index) -->
<c:otherwise>
<c:recurse>
<c:arg name="index">
<t:inc>
<c:value-of name="index" />
</t:inc>
</c:arg>
</c:recurse>
</c:otherwise>
</c:cases>
</c:let>
</function>
</section>
</package>