# 2h: Set Logic

## `+in` <a href="#in" id="in"></a>

Set operations.

Core whose arms contain a variety of functions that operate on `+set`s. Its sample accepts the input `+set` to be manipulated.

#### Accepts

A `+set`.

#### Source

```hoon
~/  %in
=|  a=(tree)
|@
```

#### Examples

```
> ~(. in (sy "asd"))
<16.ufw [a=?(%~ [?(n=@tD n=#1) l=nlr(?(@tD #1)) r=nlr(?(@tD ^#1.?(@tD #1)))]) <123.zao 46.hgz 1.pnw %140>]>
```

### `+all:in` <a href="#allin" id="allin"></a>

Logical AND.

Computes the logical AND on every element in `.a` slammed with `.b`, producing a `$flag`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a gate that accepts a `$noun` and produces a `$flag`.

#### Produces

A `$flag`.

#### Source

```hoon
++  all
  ~/  %all
  |*  b=$-(* ?)
  |-  ^-  ?
  ?~  a
    &
  ?&((b n.a) $(a l.a) $(a r.a))
```

#### Examples

```
> (~(all in (silt ~[1 2 3 4])) |=(a=@ (lth a 5)))
%.y
```

```
> (~(all in (silt ~[1 2 3 4 5])) |=(a=@ (lth a 5)))
%.n
```

***

### `+any:in` <a href="#anyin" id="anyin"></a>

Logical OR.

Computes the logical OR on every element of `.a` slammed with `.b`, producing a `$flag`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a gate that accepts a `$noun` and produces a `$flag`.

#### Produces

A `$flag`.

#### Source

```hoon
++  any
  ~/  %any
  |*  b=$-(* ?)
  |-  ^-  ?
  ?~  a
    |
  ?|((b n.a) $(a l.a) $(a r.a))
```

#### Examples

```
> (~(any in (silt ~[2 3 4 5])) |=(a=@ (lth a 3)))
%.y
```

```
> (~(any in (silt ~[3 4 5])) |=(a=@ (lth a 3)))
%.n
```

***

### `+apt:in` <a href="#aptin" id="aptin"></a>

Check correctness.

Computes whether `.a` has a correct horizontal order and a correct vertical order, producing a `$flag`.

#### Accepts

`.a` is a `+set`.

#### Produces

A `$flag`.

#### Source

```hoon
++  apt
  =<  $
  ~/  %apt
  =|  [l=(unit) r=(unit)]
  |.  ^-  ?
  ?~  a   &
  ?&  ?~(l & (gor n.a u.l))
      ?~(r & (gor u.r n.a))
      ?~(l.a & ?&((mor n.a n.l.a) $(a l.a, l `n.a)))
      ?~(r.a & ?&((mor n.a n.r.a) $(a r.a, r `n.a)))
  ==
```

#### Examples

```
> ~(apt in ~)
%.y
```

```
> =a (silt ~[1 2 3])

> a
[n=2 l={1} r={3}]

> ~(apt in a)
%.y
```

```
> =z ?~(a ~ a(n 10))

> z
[n=10 l={1} r={3}]

> ~(apt in z)
%.n
```

#### Discussion

See section [`2f`](https://docs.urbit.org/hoon/stdlib/2f) for more information on `$noun` ordering.

***

### `+bif:in` <a href="#bifin" id="bifin"></a>

Bifurcate.

Splits set `.a` into sets `.l` and `.r`, which contain the items either side of `.b` but not including `.b`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a `$noun`.

#### Produces

A cell of two `+set`s.

#### Source

```hoon
++  bif
  ~/  %bif
  |*  b=*
  ^+  [l=a r=a]
  =<  +
  |-  ^+  a
  ?~  a
    [b ~ ~]
  ?:  =(b n.a)
    a
  ?:  (gor b n.a)
    =+  c=$(a l.a)
    ?>  ?=(^ c)
    c(r a(l r.c))
  =+  c=$(a r.a)
  ?>  ?=(^ c)
  c(l a(r l.c))
```

#### Examples

```
> =a `(set @)`(silt (gulf 1 20))
> a
{17 8 20 13 11 5 19 7 15 10 18 14 6 12 9 1 2 3 16 4}

> (~(bif in a) 10)
[l=[n=11 l={17 8 20 13} r={5 19 7 15}] r=[n=12 l={18 14 6} r={9 1 2 3 16 4}]]

> `[(set @) (set @)]`(~(bif in a) 10)
[{17 8 20 13 11 5 19 7 15} {18 14 6 12 9 1 2 3 16 4}]
```

#### Discussion

Note that `+set`s are horizontally ordered by the [mug](https://docs.urbit.org/hoon/2e#mug) hash of their items and vertically ordered by the double-`+mug` hash of their items. This means bifurcating the set of numbers `(silt ~[10 20 30 40 50])` at `30` will not produce `[{10 20} {40 50}]`, but rather `[{20} {10 40 50}]` due to the tree structure resulting from their `+mug` hashes.

***

### `+del:in` <a href="#delin" id="delin"></a>

Remove `$noun`.

Removes `.b` from the `+set` `.a`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a `$noun`.

#### Produces

A `+set`.

#### Source

```hoon
++  del
  ~/  %del
  |*  b=*
  |-  ^+  a
  ?~  a
    ~
  ?.  =(b n.a)
    ?:  (gor b n.a)
      a(l $(a l.a))
    a(r $(a r.a))
  |-  ^-  [$?(~ _a)]
  ?~  l.a  r.a
  ?~  r.a  l.a
  ?:  (mor n.l.a n.r.a)
    l.a(r $(l.a r.l.a))
  r.a(l $(r.a l.r.a))
```

#### Examples

```
> `(set @)`(~(del in (silt ~[1 2 3 4 5])) 3)
{5 1 2 4}
```

```
> `(set @t)`(~(del in (silt ~['foo' 'bar' 'baz'])) 'bar')
{'baz' 'foo'}
```

```
> `(set @)`(~(del in (silt ~[1 2 3 4 5])) 10)
{5 1 2 3 4}
```

```
> `(set @)`(~(del in ~) 10)
{}
```

***

### `+dif:in` <a href="#difin" id="difin"></a>

Difference.

Computes the difference between `.a` and `.b`, producing the set of items in `.a` that are not in `.b`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a `+set`.

#### Produces

A `+set`.

#### Source

```hoon
++  dif
  ~/  %dif
  =+  b=a
  |@
  ++  $
    |-  ^+  a
    ?~  b
      a
    =+  c=(bif n.b)
    ?>  ?=(^ c)
    =+  d=$(a l.c, b l.b)
    =+  e=$(a r.c, b r.b)
    |-  ^-  [$?(~ _a)]
    ?~  d  e
    ?~  e  d
    ?:  (mor n.d n.e)
      d(r $(d r.d))
    e(l $(e l.e))
  --
```

#### Examples

```
> =a (silt ~[1 2 3 4 5])
> =b (silt ~[3 4])

> `(set @)`(~(dif in a) b)
{5 1 2}
```

***

### `+dig:in` <a href="#digin" id="digin"></a>

Address `.b` in `.a`.

Produce the tree address of `.b` within `.a`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a `$noun`.

#### Produces

The `+unit` of an `$atom`.

#### Source

```hoon
++  dig
  |=  b=*
  =+  c=1
  |-  ^-  (unit @)
  ?~  a  ~
  ?:  =(b n.a)  [~ u=(peg c 2)]
  ?:  (gor b n.a)
    $(a l.a, c (peg c 6))
  $(a r.a, c (peg c 7))
```

#### Examples

```
> =a (silt ~[1 2 3 4 5 6 7])

> -.a
n=6

> (~(dig in a) 7)
[~ 12]

> (~(dig in a) 2)
[~ 60]

> (~(dig in a) 6)
[~ 2]

> (~(dig in a) 10)
~
```

#### Discussion

For more on the tree addressing system, see section [1b](https://docs.urbit.org/hoon/stdlib/1b).

***

### `+gas:in` <a href="#gasin" id="gasin"></a>

Concatenate.

Insert the elements of a `+list` `.b` into a `+set` `.a`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a list.

#### Produces

A `+set`.

#### Source

```hoon
++  gas
  ~/  %gas
  |=  b=(list _?>(?=(^ a) n.a))
  |-  ^+  a
  ?~  b
    a
  $(b t.b, a (put i.b))
```

#### Examples

```
> =a (silt ~['foo' 'bar' 'baz'])
> `(set @t)`a
{'bar' 'baz' 'foo'}

> `(set @t)`(~(gas in a) ~['foo' 'foo' 'foo' 'foo'])
{'bar' 'baz' 'foo'}

> `(set @t)`(~(gas in a) ~['abc' 'xyz' '123'])
{'xyz' 'bar' 'baz' 'foo' 'abc' '123'}
```

***

### `+has:in` <a href="#hasin" id="hasin"></a>

Is `.b` in `.a`?

Checks if `.b` is an element of `.a`, producing a `$flag`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a `$noun`.

#### Produces

A `$flag`.

#### Source

```hoon
++  has
  ~/  %has
  |*  b=*
  ^-  ?
  %.  [~ b]
  |=  b=(unit _?>(?=(^ a) n.a))
  =>  .(b ?>(?=(^ b) u.b))
  |-  ^-  ?
  ?~  a
    |
  ?:  =(b n.a)
    &
  ?:  (gor b n.a)
    $(a l.a)
  $(a r.a)
```

#### Examples

```
> =a (silt ~[1 2 3 4 5])

> (~(has in a) 2)
%.y

> (~(has in a) 6)
%.n
```

***

### `+int:in` <a href="#intin" id="intin"></a>

Intersection.

Produces a `+set` of the intersection between two sets of the same type, `.a` and `.b`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a `+set`.

#### Produces

A `+set`.

#### Source

```hoon
++  int
  ~/  %int
  =+  b=a
  |@
  ++  $
    |-  ^+  a
    ?~  b
      ~
    ?~  a
      ~
    ?.  (mor n.a n.b)
      $(a b, b a)
    ?:  =(n.b n.a)
      a(l $(a l.a, b l.b), r $(a r.a, b r.b))
    ?:  (gor n.b n.a)
      %-  uni(a $(a l.a, r.b ~))  $(b r.b)
    %-  uni(a $(a r.a, l.b ~))  $(b l.b)
  --
```

#### Examples

```
> `(set @tD)`(~(int in (silt "foobar")) (silt "bar"))
{'r' 'b' 'a'}
```

```
> `(set @tD)`(~(int in (silt "foobar")) ~)
{}
```

```
> `(set @tD)`(~(int in (silt "foobar")) (silt "baz"))
{'b' 'a'}
```

***

### `+put:in` <a href="#putin" id="putin"></a>

Put `.b` in `.a`.

Add an element `.b` to the set `.a`, producing a `+set`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a `$noun`.

#### Produces

A `+set`.

#### Source

```hoon
++  put
  ~/  %put
  |*  b=*
  |-  ^+  a
  ?~  a
    [b ~ ~]
  ?:  =(b n.a)
    a
  ?:  (gor b n.a)
    =+  c=$(a l.a)
    ?>  ?=(^ c)
    ?:  (mor n.a n.c)
      a(l c)
    c(r a(l r.c))
  =+  c=$(a r.a)
  ?>  ?=(^ c)
  ?:  (mor n.a n.c)
    a(r c)
  c(l a(r l.c))
```

#### Examples

```
> `(set @)`(~(put in (silt ~[1 2 3])) 4)
{1 2 3 4}
```

```
> `(set @)`(~(put in `(set @)`~) 42)
{42}
```

***

### `+rep:in` <a href="#repin" id="repin"></a>

Accumulate.

Accumulate the elements of `.a` using binary gate `.b`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a gate.

#### Produces

A `$noun`.

#### Source

```hoon
++  rep
  ~/  %rep
  |*  b=_=>(~ |=([* *] +<+))
  |-
  ?~  a  +<+.b
  $(a r.a, +<+.b $(a l.a, +<+.b (b n.a +<+.b)))
```

#### Examples

```
> (~(rep in (silt ~[1 2 3 4 5])) add)
b=15
```

```
> `@t`(~(rep in (silt ~['foo' 'bar' 'baz'])) |=(a=[@ @] (cat 3 a)))
'foobarbaz'
```

***

### `+run:in` <a href="#runin" id="runin"></a>

Apply gate to set.

Produce a `+set` containing the products of gate `.b` applied to each element in `.a`.

#### Accepts

`.a` is a `+set`.

`.b` is a gate.

#### Produces

A `+set`.

#### Source

```hoon
++  run
  ~/  %run
  |*  b=gate
  =+  c=`(set _?>(?=(^ a) (b n.a)))`~
  |-  ?~  a  c
  =.  c  (~(put in c) (b n.a))
  =.  c  $(a l.a, c c)
  $(a r.a, c c)
```

#### Examples

```
> =s (silt ~["a" "A" "b" "c"])

> `(set tape)`s
{"A" "a" "c" "b"}

> (~(run in s) cuss)
{"A" "C" "B"}
```

***

### `+tap:in` <a href="#tapin" id="tapin"></a>

Set to list.

Flattens the `+set` `.a` into a `+list`.

#### Accepts

`.a` is an set.

#### Produces

A list.

#### Source

```hoon
++  tap
  =<  $
  ~/  %tap
  =+  b=`(list _?>(?=(^ a) n.a))`~
  |.  ^+  b
  ?~  a
    b
  $(a r.a, b [n.a $(a l.a)])
```

#### Examples

```
> ~(tap in (silt "foobar"))
"oafbr"
```

```
> ~(tap in (silt ~[1 2 3 4 5]))
~[4 3 2 1 5]
```

***

### `+uni:in` <a href="#uniin" id="uniin"></a>

Union.

Produces a `+set` of the union between two sets of the same type, `.a` and `.b`.

#### Accepts

`.a` is a `+set`, and is the sample of `+in`.

`.b` is a `+set`.

#### Produces

A `+set`.

#### Source

```hoon
++  uni
  ~/  %uni
  =+  b=a
  |@
  ++  $
    ?:  =(a b)  a
    |-  ^+  a
    ?~  b
      a
    ?~  a
      b
    ?:  =(n.b n.a)
      b(l $(a l.a, b l.b), r $(a r.a, b r.b))
    ?:  (mor n.a n.b)
      ?:  (gor n.b n.a)
        $(l.a $(a l.a, r.b ~), b r.b)
      $(r.a $(a r.a, l.b ~), b l.b)
    ?:  (gor n.a n.b)
      $(l.b $(b l.b, r.a ~), a r.a)
    $(r.b $(b r.b, l.a ~), a l.a)
  --
```

#### Examples

```
> =a (silt ~[1 2 3 4 5])
> =b (silt ~[4 5 6 7 8])

> `(set @)`(~(uni in a) b)
{8 5 7 6 1 2 3 4}

> `(set @)`(~(uni in a) ~)
{5 1 2 3 4}

> `(set @)`(~(uni in `(set @)`~) b)
{8 5 7 6 4}
```

***

### `+wyt:in` <a href="#wytin" id="wytin"></a>

Set size.

Produces the number of elements in set `.a` as an `$atom`.

#### Accepts

`.a` is a `+set`.

#### Produces

An `$atom`.

#### Source

```hoon
++  wyt
  =<  $
  ~%  %wyt  +  ~
  |.  ^-  @
  ?~(a 0 +((add $(a l.a) $(a r.a))))
--
```

#### Examples

```
> ~(wyt in (silt ~[1 2 3 4]))
4
```

```
> ~(wyt in `(set @)`~)
0
```

***