# Math, Numbers & Tez

LIGO offers three built-in numerical types: `int`

, `nat`

and
`tez`

. Values of type `int`

are integers; values of type `nat`

are
natural numbers (integral numbers greater than or equal to zero);
values of type `tez`

are units of measure of Tezos tokens.

- Integer literals are the same found in mainstream programming
languages, for example,
`10`

,`-6`

and`0`

, but there is only one canonical zero:`0`

(so, for instance,`-0`

and`00`

are invalid).

Natural numbers are written as digits followed by the annotation

`as nat`

, like so:`12 as nat`

,`0 as nat`

, and the same restriction on zero as integers applies:`0 as nat`

is the only way to specify the natural zero.Tezos tokens can be specified using literals of three kinds:

- units of millionth of
`tez`

, using the annotation`as mutez`

after a natural literal, like`10000 as mutez`

or`0 as mutez`

; - units of
`tez`

, using the annotation`as tez`

, like`3 as tez`

; - decimal amounts of
`tez`

are not supported by JsLIGO, instead the amount should be written as`mutez`

.

- units of millionth of

Note that large integral values can be expressed using underscores to
separate groups of digits, like `1_000 as mutez`

.

## Addition

Addition in LIGO is accomplished by means of the `+`

infix
operator. Some type constraints apply, for example you cannot add a
value of type `tez`

to a value of type `nat`

.

In the following example you can find a series of arithmetic
operations, including various numerical types. However, some bits
remain in comments as they would otherwise not compile, for example,
adding a value of type `int`

to a value of type `tez`

is invalid. Note
that adding an integer to a natural number produces an integer.

Tip: you can use underscores for readability when defining large numbers:

let sum : tez = 100_000 as mutez;

## Subtraction

Subtraction looks as follows.

⚠️ Even when subtracting two

`nats`

, the result is an`int`

.

From protocol * Ithaca* onwards subtracting values of type

`tez`

yeilds an optional value (due to the Michelson instruction
`SUB_MUTEZ`

)## Multiplication

You can multiply values of the same type, such as:

## Euclidean Division

In LIGO you can divide `int`

, `nat`

, and `tez`

. Here is how:

⚠️ Division of two

`tez`

values results into a`nat`

.

LIGO also allows you to compute the remainder of the Euclidean division. In LIGO, it is a natural number.

The behaviour of the

`%`

operator in JsLIGO is different from JavaScript. In JsLIGO,`%`

is a modulus operator and in JavaScript it's a remainder operator. In the case of positive numbers everything is the same, but not with negative numbers.

For cases when you need both the quotient and the remainder, LIGO provides the
`ediv`

operation. `ediv x y`

returns `Some (quotient, remainder)`

, unless `y`

is zero, in which case it returns `None`

## From `int`

to `nat`

and back

You can *cast* an `int`

to a `nat`

and vice versa. Here is how:

## Checking a `nat`

You can check if a value is a `nat`

by using a predefined cast
function which accepts an `int`

and returns an optional `nat`

: if the
result is not `None`

, then the provided integer was indeed a natural
number, and not otherwise.