# Architecture-independent Numeric Types

##### February 20, 2023

Go provides several predeclared numeric types. Most of them have a fixed size, regardless of the architecture the program is compiled for or running on.

## Numeric Types

An integer, floating-point, or complex type represents the set of integer, floating-point, or complex values, respectively. They are collectively called numeric types. The predeclared architecture-independent numeric types are:

``````uint8       the set of all unsigned  8-bit integers (0 to 255)
uint16      the set of all unsigned 16-bit integers (0 to 65535)
uint32      the set of all unsigned 32-bit integers (0 to 4294967295)
uint64      the set of all unsigned 64-bit integers (0 to 18446744073709551615)

int8        the set of all signed  8-bit integers (-128 to 127)
int16       the set of all signed 16-bit integers (-32768 to 32767)
int32       the set of all signed 32-bit integers (-2147483648 to 2147483647)
int64       the set of all signed 64-bit integers (-9223372036854775808 to 9223372036854775807)

float32     the set of all IEEE-754 32-bit floating-point numbers
float64     the set of all IEEE-754 64-bit floating-point numbers

complex64   the set of all complex numbers with float32 real and imaginary parts
complex128  the set of all complex numbers with float64 real and imaginary parts

byte        alias for uint8
rune        alias for int32
``````

The value of an n-bit integer is n bits wide and represented using two’s complement arithmetic.

This gives us a ton of flexibility, built right into the language. Sometimes you need even larger numbers, though, and then the standard library’s math/big package can help.

If you’re dealing with currencies, you may be tempted to use `float64` or even `float32`, but please don’t! IEEE-754 floating point numbers are not precise. And not just for really big or really small numbers. You will introduce bugs into your software by using floating point values for currency addition or other math. Instead, either use an integer type, and treat the right most digits as decimal places (usually 2 decimal places, but it depends on your currency), or use a library specifically intended for handling currency math (I don’t actually know of a good one, or I’d link to it here).

More on `byte` and `rune` later this week.

Quotes from The Go Programming Language Specification, Version of January 19, 2023

## Related Content

#### Empty structs

We finally we have enough knowledge for the EBNF format not to seem completely foreign, so let’s jump back and take a look at that, with the examples provided in the spec… Struct types … StructType = "struct" "{" { FieldDecl ";" } "}" . FieldDecl = (IdentifierList Type | EmbeddedField) [ Tag ] . EmbeddedField = [ "*" ] TypeName [ TypeArgs ] . Tag = string_lit . // An empty struct.

#### Struct tags

Struct types … A field declaration may be followed by an optional string literal tag, which becomes an attribute for all the fields in the corresponding field declaration. An empty tag string is equivalent to an absent tag. The tags are made visible through a reflection interface and take part in type identity for structs but are otherwise ignored. struct { x, y float64 "" // an empty tag string is like an absent tag name string "any string is permitted as a tag" _ [4]byte "ceci n'est pas un champ de structure" } // A struct corresponding to a TimeStamp protocol buffer.

#### Struct method promotion

Yesterday we saw an example of struct field promotion. But methods (which we haven’t really discussed yet) can also be promoted. Struct types … Given a struct type S and a named type T, promoted methods are included in the method set of the struct as follows: If S contains an embedded field T, the method sets of S and *S both include promoted methods with receiver T. The method set of *S also includes promoted methods with receiver *T.