Variables

Julia provides an extremely flexible system for naming variables. Capitalization carries no semantic meaning, nor does the first letter of a variable.

julia> ix = 1.0
1.0

julia> y = -3
-3

julia> Z = "My string"
"My string"

julia> customary_phrase = "Hello world!"
"Hello world!"

julia> UniversalDeclarationOfHumanRightsStart = "人人生而自由，在尊严和权力上一律平等。"
"人人生而自由，在尊严和权力上一律平等。"

They can even be given Unicode names:

julia> δ = 0.00001
0.00001

julia> 안녕하세요 = "Hello"
"Hello"

Julia will even let you redefine built-in constants and functions if needed:

julia> pi
π = 3.1415926535897...

julia> pi = 3
Warning: imported binding for pi overwritten in module Main
3

julia> pi
3

julia> sqrt = 4
4

However, this is obviously not recommended to avoid potential confusion.

The only explicitly disallowed names for variables are the names of built-in statements:

julia> else = false
ERROR: syntax: unexpected else

julia> try = "No"
ERROR: syntax: unexpected =

Stylistic convention

While Julia imposes few restrictions on valid names, it has become useful to adopt the following conventions on names in Julia:

• Names of variables are in lower case, with word separation indicated by underscores ('\_').
• Names of Types begin with a capital letter and word separation is shown with CamelCase instead of underscores.
• Names of functions and macros are in lower case, without underscores.
• Functions that modify their inputs have names that end in !. These functions are sometimes called mutating functions or in-place functions.