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#! /usr/bin/env slsh
% This program presents the solution to a problem posed by
% Tom Christiansen <tchrist@mox.perl.com>. The problem reads:
%
% Sort an input file that consists of lines like this
%
% var1=23 other=14 ditto=23 fred=2
%
% such that each output line is sorted WRT to the number. Order
% of output lines does not change. Resolve collisions using the
% variable name. e.g.
%
% fred=2 other=14 ditto=23 var1=23
%
% Lines may be up to several kilobytes in length and contain
% zillions of variables.
%---------------------------------------------------------------------------
%
% The solution presented below works by breaking up the line into an
% array of alternating keywords and values with the keywords as the even
% elements and the values as the odd. It is about 30% faster than the
% python solution.
private variable Keys, Values;
private define sort_fun (i, j)
{
variable s, a, b;
s = Values[i] - Values[j];
!if (s)
return strcmp (Keys[i], Keys[j]);
return s;
}
define slsh_main ()
{
variable line, len, i, vals;
foreach line (stdin)
{
line = strtok (line, " \t\n=");
len = length(line)/2;
if (len == 0)
continue;
% Even elements are keys, odd are values
Keys = line[[0::2]];
vals = line[[1::2]];
Values = atoi (vals);
i = array_sort ([0:len-1], &sort_fun);
% There are different ways of writing the result. Here is a
% fast way that avoids a loop.
() = printf ("%s\n", strjoin (Keys[i] + "=" + vals[i], " "));
}
}
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