INSERT (_) If m is a gerund, then m/y inserts successive verbs from m between items of y. Thus, +`*/i.6 is 0+1*2+3*4+5. The gerund m may extend cyclically.
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u/ (Adverb)
INSERT (_) u/y applies the dyad u between the items of y. Thus:
i.3 2 +/i.3 2 */2 3 4
0 1 6 9 24
2 3
4 5
If y has no items (that is, 0=#y), the result of u/y is the identity element of the verb u. An identity element of a function u is a value e such that either x u e is x, or e u x is x for every x in the domain (or perhaps some significant sub-domain such as boolean) of u. This definition of insertion over an argument having zero items extends partitioning identities of the form (+/y)–:(+/k{.y)+ +/k}.y to the cases k=. 0 and k=. #y.
The identity function of a verb u is a function ifu such that (ifu y)ΓÇô:(u/y) if 0=#y. The identity functions are:
$&0&}.&$ < > + ΓÇô +. ~: |
$&1&}.&$ = <: >: * % *. %: ^ !
$&_&}.&$ <.
$&__&}.&$ >.
i.&(0&,)&(2&}.)&$ ,
i.&(1&{.)&}.&$ @. {
=&i.&(1&{.)&}.&$ %. +/ . *
ifu u/
$&(v^:_1 ifu$0)&}.&$ u&.v
FUNCTION TABLE (_ _) If x and y are numeric lists, then x */ y is their multiplication table. For example:
1 2 3 */ 4 5 6 7
4 5 6 7
8 10 12 14
12 15 18 21
In general, each cell of x is applied to the entire y. Thus x u/ y is x u"(lu,_) y.