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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 59 |
1 files changed, 59 insertions, 0 deletions
@@ -18035,6 +18035,65 @@ then generalized into the floating point domain. For instance the expression yields a residue of 0.25 because 0.5 "goes into" 0.75 only once, with a "remainder" of 0.25. +.coNP Functions @ wrap and @ wrap* +.synb +.mets (wrap < start < end << number ) +.mets (wrap < start < end << number ) +.syne +.desc +The +.code wrap +and +.code wrap* +functions reduce +.meta number +into the range specified by +.meta start +and +.metn end . + +Under +.code wrap +the range is inclusive of the +.meta end +value, whereas under +.code wrap* +it is exclusive. + +The following equivalence holds + +.cblk + (wrap a b c) <--> (wrap* a (succ b) c) +.cble + +The expression +.code (wrap* x0 x1 x) +performs the following calculation: + +.cblk +.meti (+ (mod (- x x0) (- x1 x0)) x0) +.cble + +In other words, first +.meta start +is subtracted from +.metn number . +Then the result is reduced modulo the displacement +between +.code start +and +.codn end . +Finally, +.meta start +is added back to that result, which is returned. + +.TP* Example: + +.cblk + ;; perform ROT13 on the string "nop" + [mapcar (opip (+ 13) (wrap #\ea #\ez)) "nop"] -> "abc" +.cble + .coNP Functions @ gcd and @ lcm .synb .mets (gcd << number *) |