# Vocabulary/starco

 *: 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.)