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recursive-graph-body-print
Function
The graph-body-print
function may also be written recursively.
The recursive solution is divided into two parts: an outside `wrapper'
that uses a let
expression to determine the values of several
variables that need only be found once, such as the maximum height of
the graph, and an inside function that is called recursively to print
the graph.
The `wrapper' is uncomplicated:
(defun recursive-graph-body-print (numbers-list) "Print a bar graph of the NUMBERS-LIST. The numbers-list consists of the Y-axis values." (let ((height (apply 'max numbers-list)) (symbol-width (length graph-blank)) from-position) (recursive-graph-body-print-internal numbers-list height symbol-width))) |
The recursive function is a little more difficult. It has four parts:
the `do-again-test', the printing code, the recursive call, and the
`next-step-expression'. The `do-again-test' is an if
expression that determines whether the numbers-list
contains
any remaining elements; if it does, the function prints one column of
the graph using the printing code and calls itself again. The
function calls itself again according to the value produced by the
`next-step-expression' which causes the call to act on a shorter
version of the numbers-list
.
(defun recursive-graph-body-print-internal (numbers-list height symbol-width) "Print a bar graph. Used within recursive-graph-body-print function." (if numbers-list (progn (setq from-position (point)) (insert-rectangle (column-of-graph height (car numbers-list))) (goto-char from-position) (forward-char symbol-width) (sit-for 0) ; Draw graph column by column. (recursive-graph-body-print-internal (cdr numbers-list) height symbol-width)))) |
After installation, this expression can be tested; here is a sample:
(recursive-graph-body-print '(3 2 5 6 7 5 3 4 6 4 3 2 1)) |
Here is what recursive-graph-body-print
produces:
* ** * **** * **** *** * ********* ************ ************* |
Either of these two functions, graph-body-print
or
recursive-graph-body-print
, create the body of a graph.
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Copyright © 2003 by The Free Software Foundation | Updated Jun 2003 |