| --- |
| title: Iota |
| --- |
| |
| ## Summary |
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| Go's ` iota ` identifier is used in ` const ` declarations to simplify definitions of incrementing numbers. Because it can be used in expressions, it provides a generality beyond that of simple enumerations. |
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| The value of iota is reset to 0 whenever the reserved word ` const ` appears in the source (i.e. each const block) and incremented by one after each [ConstSpec](https://go.dev/ref/spec#ConstSpec) e.g. each Line. This can be combined with the constant shorthand (leaving out everything after the constant name) to very concisely define related constants. |
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| Iota: https://go.dev/ref/spec#Iota |
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| Constant declarations: https://go.dev/ref/spec#Constant_declarations |
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| ## Examples |
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| The official spec has two great examples: |
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| https://go.dev/ref/spec#Iota |
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| Here's one from Effective Go: |
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| ``` |
| type ByteSize float64 |
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| const ( |
| _ = iota // ignore first value by assigning to blank identifier |
| KB ByteSize = 1 << (10 * iota) |
| MB |
| GB |
| TB |
| PB |
| EB |
| ZB |
| YB |
| ) |
| ``` |
| |
| Weekday enum example - How iota is calculated - From [Learn Go Programming Blog](https://blog.learngoprogramming.com): |
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|  |
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| ## Articles |
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| * [Ultimate Visual Guide to Go Enums and Iota](https://blog.learngoprogramming.com/golang-const-type-enums-iota-bc4befd096d3) _2017-10-09_ |
