continue

Case Study 2: Complex String Handling
Quasi-string/Quasi-list syntax lighten code

Key Idea: Quasi-strings: {7 * 8 = [(* 7 8)]}
{} indicates string, [] escapes out to Scheme.
Easy to learn/use, clearly lightens code. 
; generate HTML histogram table from results of DB query
(define (histogram field table)
   (define results
      (dbquery
          {select [field],count(*) from [table] 
            group by [field], order by [field] asc}))




   {<html><body>
      <h1>Query results</h1>
      The result of query <pre>[s]</pre> is 
      <table> [(trs results)]</table>
      </body></html>})

(define (trs rows) (map (lambda (row) {<tr> [(tds row)]</tr>\n}) rows))
(define (tds row)  (map (lambda (col) {<td> [   col   ]</td>}) row))
Similar Scheme approaches: SCRIBE (Serrano), BRL (Lewis), ...
continue

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LL2, Saturday 9 November 2002, Tim Hickey/Ken Anderson