| p {~ q i. ] Improved |
initial writing: 2006-11-07 last updated: 2007-11-29 |
The monad p {~ q i. ] where p and q are lists of 1-byte characters performs character mappings. For example:
'AA aa'=: a.{~ 65 97 +/ i.26
AA
ABCDEFGHIJKLMNOPQRSTUVWXYZ
aa
abcdefghijklmnopqrstuvwxyz
lc=: (aa,a.) {~ (AA,a.) i. ]
lc 'United States of America, Union of South Africa'
united states of america, union of south africa
The phrase and its variants ( (q i.]){p"_ and q&i.{p"_ ) are now supported by special code and are faster and leaner. The following benchmarks demonstrate the improvement:
x=: a. {~ 1e6 ?@$ 256
p=: a. {~ 123 (22 b.) i.256
ts=: 6!:2, 7!:2@] NB. time and space
ts 'Expression'
| Expression | J 6.02 | J 6.01 | Ratio | |||||||||
| lc x | 0.004747 | 1.04934e6 | 0.018244 | 9.43795e6 | 3.84 | 8.99 | ||||||
| (p{~a.i.]) x | 0.001450 | 1.04979e6 | 0.018401 | 9.43840e6 | 12.69 | 8.99 | ||||||