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Diffstat (limited to 'libslang/examples/sort.sl')
-rw-r--r-- | libslang/examples/sort.sl | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/libslang/examples/sort.sl b/libslang/examples/sort.sl new file mode 100644 index 0000000..c2eb7ad --- /dev/null +++ b/libslang/examples/sort.sl @@ -0,0 +1,62 @@ +#! /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. + +static variable Keys, Values; +static 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 main () +{ + variable line, len, i, vals; + foreach (stdin) + { + line = (); + 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 = array_map(Int_Type, &integer, 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], " ")); + } +} + +main (); |