urbit/base/pub/doc/hoon/runes/ts/tsgr.md

tisgar, =>, %tsgr

Product as subject

=> is a natural rune that uses the product of p as the subject of q. => is the inverse of =<. Use => when your p isn't too long and => makes for more readable code.

See also

tisgal, =<, %tsgl

Produces

Twig: [%tsgr p=twig q=twig]

Sample

p and q are twigs.

Tall form

=>  p
    q

Wide form

=>(p q)

Irregular form

None

Examples

~zod/try=> =>([a=1 b=2 c=3] b)
2
~zod/try=> =>((add 2 4) [. .])
[6 6]

In this simple example we first produce b from the tuple [a=1 b=2 c=3] using the wide form of =>. Then we use . to produce our context from the computation (add 2 4) as a cell, [6 6].

~zod/try=> 
=cor  |=  a=@
      =+  b=0
      =>  .(b (add 2 b))
      =>  .(a (add a b))
      [a b]
new var %cor
/~zod/try=> 
(cor 4)
[6 2]

Here we see a common pattern for using => to conduct procedural changes to values in our subject. First we replace b with b+2 using the irregular form of %-, then we replace a with the sum of a and b the same way.