Index mapping: Difference between revisions

Revision as of 02:33, 14 December 2012

Revision as of 09:29, 2 September 2013

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This example<ref>[http://ols.fedoraproject.org/GCC/Reprints-2008/sayle-reprint.pdf "A Superoptimizer Analysis of Multiway Branch Code Generation"] by Roger Anthony Sayle</ref> of a C function – returning TRUE if a month (x) contains 30 days (otherwise FALSE), illustrates the concept succinctly

<source lang="c">

if (((unsigned)x > 12) return 0; || ((unsigned)x <= 0) return 0; /*x>12 or x<=0?*/

static const int T[12] ={0,0,0,1,0,1,0,0,1,0,1,0}; /* 0-based table 'if 30 days =1,else 0' */

return T[x - 1]; /* return with boolean 1 = true, 0=false */

</source>