Variable

As explained in Julia as a Second Language

A variable is a named binding that associates an identifier with a value or other computation during program execution.

A variable gives a value a name so you can reuse it in a calculation instead of repeatedly typing the value. In Julia, write `y = 7` to bind the identifier `y` to `7`. Then `z = 3` and `y + z + 2` produce `12`. section 2.2

The `=` operator binds a name to a value; `==` compares expressions for equality. A variable can be rebound: after `x = 2`, evaluating `x = x + 3` leaves `x` bound to `5`. Think of this as moving a name from the old result to the new one, rather than changing a number inside a fixed slot. section 2.2.1 section 2.7

Figure 2.2 Binding variable x to different memory locations

The diagram follows the `x` label as it moves from the original value to the result of `x + 3`. section 2.2.1

A constant also gives a value a name, but unlike a variable, it is not meant to be changed; declare one with `const`. Identifiers are case-sensitive, so `foo` and `Foo` are different names. Reserved words such as `if`, `while`, and `const` cannot be variable names. section 2.2

How Julia as a Second Language covers it

How deep it goes

Works through binding and rebinding with a memory-label analogy, contrasting them with fixed-slot assignment in C/C++.

Examples

Uses Julia REPL calculations with `y` and `z`, then rebinds `x` from `2` to `5`.

What it assumes

Starts with basic numbers and calculations, introducing identifiers and binding through short Julia REPL examples.

What you can do after

Practice/perform naming values, reusing them in arithmetic, and rebinding variables in Julia.

How it connects

Connects variables to constants, identifiers, functions, assignment, equality comparison, and dynamically typed languages.

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Related concepts

• literalcontrasts with · A literal is a language construct that directly denotes a fixed value or specifies an exact value permitted by a type.
• let keywordused by · A let construct is a language feature that introduces a name binding associating an identifier with a value or expression.
• assignmentused by · Assignment is a programming-language operation that binds or stores an evaluated value in a variable, property, or other assignable location.
• SET statementconfigured by · A SET statement is an SQL statement that assigns values to variables or configures database or session settings.
• having clauseused by · A HAVING clause is a SQL clause that filters groups or aggregate results according to a condition.

This explainer was generated by Manning's knowledge graph from the text of Julia as a Second Language. The section links point to the parts of the book it draws on.