AligningStrings - Cookbook - s c h e m a t i c s : c o o k b o o k

Aligning Strings

Problem

You want to align a string, left, right, or center. You might use this when generating reports, for example.

Solution

The easiest solution is in SRFI-13, which solves the left and right padding issues.

>(for-each display 
          (list "|" (string-pad "Title" 20) 
                "|" (string-pad-right "Price" 10) "|"))
|               Title|Price     |

string-pad and string-pad-right both default to using #\space (the space character) as the padding character; you may override this by providing the character in the third argument. Both functions also truncate the string provided if it's longer than the specified field width. There's no definition for string-pad-center, though this is one way to do it:

(require (lib "etc.ss"))
(define string-pad-center 
    (opt-lambda (a-string width (pad-char #\space))
    (let* ((field-width (min width (string-length a-string)))
           (rmargin (floor (/ (- width field-width) 2))))
      (string-pad (string-pad-right a-string (- width rmargin) pad-char) 
                  width pad-char))))

This function returns a string of a minimum width equal to the length of a-string. If the width argument minus (string-length a-string) is odd, the extra blank space will be put on the right side of a-string. And, as with the other string-pad functions, it will truncate a-string if it's shorter than width, in this case, it will truncate on the right, e.g.

> (string-pad-center "Author" 5)
"Autho"
> (string-pad-center "Author" 10)
"  Author  "
> (string-pad-center "Author" 11 #\*)
"**Author***"

Contributors

-- GordonWeakliem - 05 Apr 2004

Comments

CookbookForm
TopicType:	Recipe
ParentTopic:	StringRecipes
TopicOrder:	120

Current Rev: r1.12 - 08 Sep 2004 - 17:48 GMT - GordonWeakliem, Revision History:Diffs | r1.12 | > | r1.11 | > | r1.10

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