How to Efficiently Skip Values Using Iota in Go Constants?

How to Efficiently Skip Values When Defining Constants with Iota in Go?

In Go, iota is a constant generator that allows you to define multiple constants sequentially. However, what if you need to skip a significant number of values during this process?

Single Group, Manual Offset

The simplest approach is to shift the iota with a constant, leaving subsequent initialization expressions empty. For instance:

const (
    APPLE = iota
    ORANGE
    PEAR
    BANANA = iota + 96 // 96 is manually calculated to get 99
    GRAPE
)

This will skip 96 values before assigning 99 to BANANA. However, note that adding elements before BANANA will affect the values of BANANA and subsequent constants.

Breaking the Constant Group

If you need to avoid this dependency, you can break the constant group and start a new one. Iota's value is reset to 0 upon encountering the reserved word const. For example:

const (
    APPLE = iota
    ORANGE
    PEAR
)
const (
    BANANA = iota + 99 // iota is reset to 0
    GRAPE
)

This method ensures that inserting elements before BANANA will not alter the values of BANANA and subsequent constants.

Single Group, Automatic Offset

To maintain a single constant group while skipping values, introduce a constant where you want to break the numbering. Subtract its value from iota in the subsequent line.

const (
    APPLE = iota
    ORANGE
    PEAR

    _BREAK

    BANANA = iota - _BREAK + 98 // Continues from 98 + 1 = 99
    GRAPE
)

Alternatively, you can initialize _BREAK with iota 1, making the offset to be applied the value of _BREAK itself.

const (
    APPLE = iota
    ORANGE
    PEAR

    _BREAK = iota + 1

    BANANA = iota - _BREAK + 99 // Continues from 99
    GRAPE
)

Select the approach that best suits your code structure and preferences to efficiently skip values when defining constants with iota in Go.

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