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eintr: Graphing words in defuns

 
 C.4.2 Graphing Numbers of Words and Symbols
 -------------------------------------------
 
 Now for the graph for which all this code was written: a graph that
 shows how many function definitions contain fewer than 10 words and
 symbols, how many contain between 10 and 19 words and symbols, how many
 contain between 20 and 29 words and symbols, and so on.
 
    This is a multi-step process.  First make sure you have loaded all
 the requisite code.
 
    It is a good idea to reset the value of ‘top-of-ranges’ in case you
 have set it to some different value.  You can evaluate the following:
 
      (setq top-of-ranges
       '(10  20  30  40  50
         60  70  80  90 100
        110 120 130 140 150
        160 170 180 190 200
        210 220 230 240 250
        260 270 280 290 300)
 
 Next create a list of the number of words and symbols in each range.
 
 Evaluate the following:
 
      (setq list-for-graph
             (defuns-per-range
               (sort
                (recursive-lengths-list-many-files
                 (directory-files "/usr/local/emacs/lisp"
                                  t ".+el$"))
                '<)
               top-of-ranges))
 
 On my old machine, this took about an hour.  It looked though 303 Lisp
 files in my copy of Emacs version 19.23.  After all that computing, the
 ‘list-for-graph’ had this value:
 
      (537 1027 955 785 594 483 349 292 224 199 166 120 116 99
      90 80 67 48 52 45 41 33 28 26 25 20 12 28 11 13 220)
 
 This means that my copy of Emacs had 537 function definitions with fewer
 than 10 words or symbols in them, 1,027 function definitions with 10 to
 19 words or symbols in them, 955 function definitions with 20 to 29
 words or symbols in them, and so on.
 
    Clearly, just by looking at this list we can see that most function
 definitions contain ten to thirty words and symbols.
 
    Now for printing.  We do _not_ want to print a graph that is 1,030
 lines high ... Instead, we should print a graph that is fewer than
 twenty-five lines high.  A graph that height can be displayed on almost
 any monitor, and easily printed on a sheet of paper.
 
    This means that each value in ‘list-for-graph’ must be reduced to
 one-fiftieth its present value.
 
    Here is a short function to do just that, using two functions we have
 not yet seen, ‘mapcar’ and ‘lambda’.
 
      (defun one-fiftieth (full-range)
        "Return list, each number one-fiftieth of previous."
       (mapcar (lambda (arg) (/ arg 50)) full-range))
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