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Basics

Go Constants

Using Constants

Go constants use const for immutable values with type inference.

Introduction to Go Constants

In Go, constants are immutable values that can be defined using the const keyword. Unlike variables, constants cannot be changed once assigned. They are evaluated at compile-time, which makes them efficient for performance-critical applications.

Go supports both typed and untyped constants, providing flexibility in how constants are used in your programs.

Defining Constants in Go

To declare a constant in Go, you use the const keyword followed by the name of the constant, an optional type, and a value. Here is the basic syntax:

const name [type] = value

If no type is specified, Go will infer the type based on the value.

Typed vs Untyped Constants

Typed constants have a specific type and must be used in expressions that are compatible with that type. Untyped constants, on the other hand, do not have a fixed type until they are used in a context that requires a specific type.

Here's an example of a typed and an untyped constant:

Constant Expressions

Constants in Go can also be the result of constant expressions. These expressions are evaluated at compile-time and can include arithmetic operations, function calls to unsafe.Sizeof, len, and cap (when applied to an array or slice), and other constants.

Multiple Constant Declarations

Go allows you to declare multiple constants at once using a block, which can be more concise and improve code readability.

Enumerated Constants Using iota

The iota identifier is used in Go to simplify the creation of incrementing numbers. It is often used to create enumerated constants, where each constant in a block is automatically assigned an incrementing integer value starting from zero.

Best Practices for Using Constants

  • Use constants for values that do not change and are used multiple times throughout your program.
  • Prefer untyped constants when flexibility with the type is desired.
  • Use iota for creating readable enumerated constants.
  • Group related constants using a block to enhance readability.

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