Letter frequency: Difference between revisions

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 =={{header|jq}}==
 The following program will report the frequency of all characters in the input file, including newlines, returns, etc, provided the file will fit in memory.<lang jq>
+# This function uses an object as a hash table for integers.
-# Input: an array
-# Output: an array of [item, count] for each run
+# The input is an array of int;
+# the output is an object with the imploded values as keys,
-def runs:
+# the values of which are the corresponding frequencies.
-  reduce .[] as $item
+def count:
-    ( [];
+  map( [.] | implode )
-      if . == [] then [ [ $item, 1] ]
-      else  .[-1] as $last
+  | reduce .[] as $item ( {}; .[$item] += 1 ) ;
-            | if $last[0] == $item
-              then (.[0:length-1] + [ [$item, $last[1] + 1] ] )
-              else . + [[$item, 1]]
-              end
-      end ) ;
+# For neatness we sort the keys:
-explode | sort | runs | map( [ ( [.[0]] | implode) , .[1] ] ) | .[]</lang>
+explode | count | . as $counts | keys | sort[] | [., $counts[.] ]
+</lang>
 Example:<lang sh>jq -s -R -c -f Letter_frequency.jq somefile.txt</lang>
 {{Out}}