Hook
< Help(Redirected from Help/Primer/Hook)
Jump to navigation
Jump to search
A train is a sequence of two or three words in a row that is given a special meaning. A train of two verbs is a hook and is evaluated as follows:
(f g) y evaluates as y f g y x (f g) y evaluates as x f g y
Suppose you wanted to scale a list of numbers such that the result was each number divided by the maximum number in the list. The maximum over a list is given by the verb derived by applying the adverb / to the verb >. .
a =. 3 5 8 2 7 maxover =. >./ maxover a 8
To divide an argument by the maximum over the argument you can use:
a % maxover a 0.375 0.625 1 0.25 0.875
The above can be written as a hook.
(% maxover) a 0.375 0.625 1 0.25 0.875
You can now define scale as a hook with % >./ .
scale =. % >./ scale a 0.375 0.625 1 0.25 0.875
Primer Index Hover to reveal titles - Click to access - Current page is highlighted | ||||||||||||||||||||||||
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | ✅ |
26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | ✅ | ||||||
45 | 46 | 47 | 48 | ✅ | ||||||||||||||||||||
50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | ✅ | ||||||||||||||||
59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | ✅ | |||||||
77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | ✅ | |||||
97 | 98 | 99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | ✅ |