@ Atop

>> << Usr Pri JfC LJ Phr Dic Voc !: Help Dictionary

Atop u@v mv lv rv

u@v y ↔ u v y .For example, +:@- 7 is _14 (double the negation). Moreover, the monadic uses of u@v and u&v are equivalent.
x u@v y ↔ u x v y . For example, 3 +:@- 7 is _8 (double the difference).

Because adverbs and conjunctions are (as stated more precisely in Section II E) executed before verbs, phrases involving them are commonly used in trains without parentheses. For example:

 mean=: +/ % #
 mean 1 2 3 4
2.5
 f=: +:@*: +/ -:@%: NB. Addition table of doubled square and halved sqrt
 f 1 2 3 4
 2.5 2.70711 2.86603 3
 8.5 8.70711 8.86603 9
18.5 18.7071 18.866 19
32.5 32.7071 32.866 33

Because a conjunction applies to the entity immediately to its right, expressions to the right of conjunctions commonly require parenthesization. For example:

 g=: *:@(+/)
 h=: *:@+/
 g 1 2 3 4
100
 h 1 2 3 4
6770404
 k=: *:@+
 k/ 1 2 3 4
6770404

Compare the behaviour of @ with that of @: . They differ only in the ranks of the verbs that they produce.

>> << Usr Pri JfC LJ Phr Dic Voc !: Help Dictionary