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doc neaten

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John Kerl 2016-04-13 23:41:26 -04:00
parent 54cacc39d6
commit 8ca1bae4f4
2 changed files with 16 additions and 40 deletions
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30
doc/content-for-reference.html
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@ -1337,35 +1337,21 @@ by design handles heterogenous data: the running <tt>@sum</tt> in
<tt>mlr put '@sum += $x'</tt>
should not be invalidated for records which have no <tt>x</tt>.
<li/> Absent out-of-stream-variable values are precisely what allow you to write not
<tt>mlr put 'begin{@sum = 0}; @sum += $x'</tt>
but rather
<tt>mlr put '@sum += $x'</tt>
&mdash; and furthermore make it possible for you to write
<tt>mlr put '@sum[$a] += $x'</tt>
at all.
<li/> Absent out-of-stream-variable values are precisely what allow you to write
<tt>mlr put '@sum += $x'</tt>. Otherwise you would have to write
<tt>mlr put 'begin{@sum = 0}; @sum += $x'</tt> &mdash;
which is tolerable &mdash; but for
<tt>mlr put 'begin{...}; @sum[$a][$b] += $x'</tt>
you&rsquo;d have to pre-initialize <tt>@sum</tt> for all values of <tt>$a</tt> and <tt>$b</tt> in your
input data stream, which is intolerable.
<!--
xxx merge
<p/>Without uninit, for the
former you&rsquo;d need to type <tt>mlr put -q 'begin{@sum = 0}; @sum += $x';
end{emit @sum}'</tt> (which is tolerable), but for the latter you&rsquo;d need
to know all values of <tt>$a</tt> and <tt>$b</tt> before reading your input
data, which would be intolerable.
-->
<li/> The penalty for this is that misspelled variables can be hard to find:
<li/> The penalty for the absent feature is that misspelled variables can be hard to find:
e.g. in <tt>mlr put 'begin{@sumx = 10}; ...; update @sumx somehow per-record; ...; end {@something = @sum * 2}'</tt>
the accumulator is spelt <tt>@sumx</tt> in the begin-block but <tt>@sum</tt> in the end-block, where since it
is absent, <tt>@sum*2</tt> evaluates to 2.
</ul>
<!--
<p/>xxx keep typing up from here.
-->
<!--
xxx say what for logical/bitwise
<p/>xxx

26
doc/reference.html
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@ -4913,25 +4913,15 @@ by design handles heterogenous data: the running <tt>@sum</tt> in
<tt>mlr put '@sum += $x'</tt>
should not be invalidated for records which have no <tt>x</tt>.
<li/> Absent out-of-stream-variable values are precisely what allow you to write not
<tt>mlr put 'begin{@sum = 0}; @sum += $x'</tt>
but rather
<tt>mlr put '@sum += $x'</tt>
&mdash; and furthermore make it possible for you to write
<tt>mlr put '@sum[$a] += $x'</tt>
at all.
<li/> Absent out-of-stream-variable values are precisely what allow you to write
<tt>mlr put '@sum += $x'</tt>. Otherwise you would have to write
<tt>mlr put 'begin{@sum = 0}; @sum += $x'</tt> &mdash;
which is tolerable &mdash; but for
<tt>mlr put 'begin{...}; @sum[$a][$b] += $x'</tt>
you&rsquo;d have to pre-initialize <tt>@sum</tt> for all values of <tt>$a</tt> and <tt>$b</tt> in your
input data stream, which is intolerable.
<!--
vxx merge
<p/>Without uninit, for the
former you&rsquo;d need to type <tt>mlr put -q 'begin{@sum = 0}; @sum += $x';
end{emit @sum}'</tt> (which is tolerable), but for the latter you&rsquo;d need
to know all values of <tt>$a</tt> and <tt>$b</tt> before reading your input
data, which would be intolerable.
-->
<li/> The penalty for this is that misspelled variables can be hard to find:
<li/> The penalty for the absent feature is that misspelled variables can be hard to find:
e.g. in <tt>mlr put 'begin{@sumx = 10}; ...; update @sumx somehow per-record; ...; end {@something = @sum * 2}'</tt>
the accumulator is spelt <tt>@sumx</tt> in the begin-block but <tt>@sum</tt> in the end-block, where since it
is absent, <tt>@sum*2</tt> evaluates to 2.