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2 f/\y Improved

initial writing: 2005-06-08 last updated: 2005-06-09

2 f/\y is now implemented by special code for any verb f and any array y , removing the previous restrictions on f and y . The table below presents time and space comparisons; the bottom section of the table shows that 2 f/\x is more efficient in time and space than the equivalent (}:x) f (}.x) .

i=: 1e5 3 ?.@$ 10           integer
x=: o. i                    floating point
b=: 1e5 3 ?.@$ 2            boolean

ts=: 6!:2 , 7!:2@]          time and space
ts 'Expression'

Expression		J 6.01				J 5.04				Ratio
2 -:/\ i		0.00095811		1.325440e5		0.13497488		3.278720e6		140.88		24.74
2 -:/\ x		0.00365637		1.325440e5		0.14033382		5.375872e6		38.38		40.56
2 -:/\ b		0.00204922		6.568320e5		0.13355729		1.705792e6		65.17		2.60
2 -.@-:/\ i		0.00095596		1.328640e5		0.17538999		3.279104e6		183.47		24.68
2 -.@-:/\ x		0.00354134		1.328640e5		0.18362529		5.376256e6		51.85		40.46
2 -.@-:/\ b		0.00201308		6.571520e5		0.17742993		1.706176e6		88.14		2.60
(}: -:"_1 }.) i		0.00460509		4.326720e6		0.00476343		4.326720e6
(}: -:"_1 }.) x		0.01125429		8.521024e6		0.01176834		8.521024e6
(}: -:"_1 }.) b		0.00256332		1.180992e6		0.00249425		1.180992e6

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