# Vocabulary/starco

From J Wiki

>>
<< ` `
Down to: Dyad ` `
Back to: Vocabulary
Thru to: Dictionary

`*: y`Square

Rank 0 *-- operates on individual atoms of y, producing a result of the same shape --*
WHY IS THIS IMPORTANT?

Equivalent to `y ^ 2`, the *square* of numeric noun `y`.

*: 7 49

### Common Uses

Can lead to neater tacit expressions

pythag=: +&.*: NB. instead of: ((x^2) + (y^2))^0.5 3 pythag 4 5

### Related Primitives

Double (`+: y`),
Halve (`-: y`),
Square Root (`%: y`)

`x *: y`Not-And

Rank 0 0 *-- operates on individual atoms of x and y, producing a result of the same shape --*
WHY IS THIS IMPORTANT?

The logical operation *Not-And* between two Boolean nouns `x` and `y`, which is false (`0`) if `x` and `y` are both true (`1`).

in other words, the same as -. x *. y

0 0 1 1 *: 0 1 0 1 1 1 1 0 (0 1) *:/ (0 1) NB. Truth-table of: *: 1 1 1 0 (0 1) *:table (0 1) NB. Truth-table with borders +--+---+ |*:|0 1| +--+---+ |0 |1 1| |1 |1 0| +--+---+

**Note:**
`*:` is restricted to Boolean arguments:

1 *: 2 |domain error | 1 *:2

### Related Primitives

Or (`x +. y`),
Not-Or (`x +: y`),
LCM (And) (`x *. y`),
Not (`-. y`),
Boolean Functions (`m b.`)