/Elixir 1.9

# Integer

Functions for working with integers.

Some functions that work on integers are found in `Kernel`:

# Summary

## Guards

is_even(integer)

Determines if an `integer` is even.

is_odd(integer)

Determines if `integer` is odd.

## Functions

digits(integer, base \\ 10)

Returns the ordered digits for the given `integer`.

floor_div(dividend, divisor)

Performs a floored integer division.

gcd(integer1, integer2)

Returns the greatest common divisor of the two given integers.

mod(dividend, divisor)

Computes the modulo remainder of an integer division.

parse(binary, base \\ 10)

Parses a text representation of an integer.

to_charlist(integer)

Returns a charlist which corresponds to the text representation of the given `integer`.

to_charlist(integer, base)

Returns a charlist which corresponds to the text representation of `integer` in the given `base`.

to_string(integer)

Returns a binary which corresponds to the text representation of `integer`.

to_string(integer, base)

Returns a binary which corresponds to the text representation of `integer` in the given `base`.

undigits(digits, base \\ 10)

Returns the integer represented by the ordered `digits`.

# is_even(integer)

(macro)

Determines if an `integer` is even.

Returns `true` if the given `integer` is an even number, otherwise it returns `false`.

Allowed in guard clauses.

#### Examples

```iex> Integer.is_even(10)
true

iex> Integer.is_even(5)
false

iex> Integer.is_even(-10)
true

iex> Integer.is_even(0)
true```

# is_odd(integer)

(macro)

Determines if `integer` is odd.

Returns `true` if the given `integer` is an odd number, otherwise it returns `false`.

Allowed in guard clauses.

#### Examples

```iex> Integer.is_odd(5)
true

iex> Integer.is_odd(6)
false

iex> Integer.is_odd(-5)
true

iex> Integer.is_odd(0)
false```

# digits(integer, base \\ 10)

`digits(integer(), pos_integer()) :: [integer(), ...]`

Returns the ordered digits for the given `integer`.

An optional `base` value may be provided representing the radix for the returned digits. This one must be an integer >= 2.

#### Examples

```iex> Integer.digits(123)
[1, 2, 3]

iex> Integer.digits(170, 2)
[1, 0, 1, 0, 1, 0, 1, 0]

iex> Integer.digits(-170, 2)
[-1, 0, -1, 0, -1, 0, -1, 0]```

# floor_div(dividend, divisor)

(since 1.4.0)
`floor_div(integer(), neg_integer() | pos_integer()) :: integer()`

Performs a floored integer division.

Raises an `ArithmeticError` exception if one of the arguments is not an integer, or when the `divisor` is `0`.

`Integer.floor_div/2` performs floored integer division. This means that the result is always rounded towards negative infinity.

If you want to perform truncated integer division (rounding towards zero), use `Kernel.div/2` instead.

#### Examples

```iex> Integer.floor_div(5, 2)
2
iex> Integer.floor_div(6, -4)
-2
iex> Integer.floor_div(-99, 2)
-50```

# gcd(integer1, integer2)

(since 1.5.0)
`gcd(integer(), integer()) :: non_neg_integer()`

Returns the greatest common divisor of the two given integers.

The greatest common divisor (GCD) of `integer1` and `integer2` is the largest positive integer that divides both `integer1` and `integer2` without leaving a remainder.

By convention, `gcd(0, 0)` returns `0`.

#### Examples

```iex> Integer.gcd(2, 3)
1

iex> Integer.gcd(8, 12)
4

iex> Integer.gcd(8, -12)
4

iex> Integer.gcd(10, 0)
10

iex> Integer.gcd(7, 7)
7

iex> Integer.gcd(0, 0)
0```

# mod(dividend, divisor)

(since 1.4.0)
`mod(integer(), neg_integer() | pos_integer()) :: integer()`

Computes the modulo remainder of an integer division.

`Integer.mod/2` uses floored division, which means that the result will always have the sign of the `divisor`.

Raises an `ArithmeticError` exception if one of the arguments is not an integer, or when the `divisor` is `0`.

#### Examples

```iex> Integer.mod(5, 2)
1
iex> Integer.mod(6, -4)
-2```

# parse(binary, base \\ 10)

`parse(binary(), 2..36) :: {integer(), binary()} | :error`

Parses a text representation of an integer.

An optional `base` to the corresponding integer can be provided. If `base` is not given, 10 will be used.

If successful, returns a tuple in the form of `{integer, remainder_of_binary}`. Otherwise `:error`.

Raises an error if `base` is less than 2 or more than 36.

If you want to convert a string-formatted integer directly to an integer, `String.to_integer/1` or `String.to_integer/2` can be used instead.

#### Examples

```iex> Integer.parse("34")
{34, ""}

iex> Integer.parse("34.5")
{34, ".5"}

iex> Integer.parse("three")
:error

iex> Integer.parse("34", 10)
{34, ""}

iex> Integer.parse("f4", 16)
{244, ""}

iex> Integer.parse("Awww++", 36)
{509216, "++"}

iex> Integer.parse("fab", 10)
:error

iex> Integer.parse("a2", 38)
** (ArgumentError) invalid base 38```

# to_charlist(integer)

`to_charlist(integer()) :: charlist()`

Returns a charlist which corresponds to the text representation of the given `integer`.

Inlined by the compiler.

#### Examples

```iex> Integer.to_charlist(123)
'123'

iex> Integer.to_charlist(+456)
'456'

iex> Integer.to_charlist(-789)
'-789'

iex> Integer.to_charlist(0123)
'123'```

# to_charlist(integer, base)

`to_charlist(integer(), 2..36) :: charlist()`

Returns a charlist which corresponds to the text representation of `integer` in the given `base`.

`base` can be an integer between 2 and 36.

Inlined by the compiler.

#### Examples

```iex> Integer.to_charlist(100, 16)
'64'

iex> Integer.to_charlist(-100, 16)
'-64'

iex> Integer.to_charlist(882_681_651, 36)
'ELIXIR'```

# to_string(integer)

`to_string(integer()) :: String.t()`

Returns a binary which corresponds to the text representation of `integer`.

Inlined by the compiler.

#### Examples

```iex> Integer.to_string(123)
"123"

iex> Integer.to_string(+456)
"456"

iex> Integer.to_string(-789)
"-789"

iex> Integer.to_string(0123)
"123"```

# to_string(integer, base)

`to_string(integer(), 2..36) :: String.t()`

Returns a binary which corresponds to the text representation of `integer` in the given `base`.

`base` can be an integer between 2 and 36.

Inlined by the compiler.

#### Examples

```iex> Integer.to_string(100, 16)
"64"

iex> Integer.to_string(-100, 16)
"-64"

iex> Integer.to_string(882_681_651, 36)
"ELIXIR"```

# undigits(digits, base \\ 10)

`undigits([integer()], pos_integer()) :: integer()`

Returns the integer represented by the ordered `digits`.

An optional `base` value may be provided representing the radix for the `digits`. Base has to be an integer greater than or equal to `2`.

#### Examples

```iex> Integer.undigits([1, 2, 3])
123

iex> Integer.undigits([1, 4], 16)
20

iex> Integer.undigits([])
0```