Conditions

If expression

if expressions are pretty straightforward and similar to most other languages. Unlike other C-like languages, there are no parentheses surrounding the condition and the braces are always required.

a := 10 b := 20 if a < b { println('${a} < ${b}') } else if a > b { println('${a} > ${b}') } else { println('${a} == ${b}') } // 10 < 20

if can be used as an expression, last expression is the value of a block:

num := 777 s := if num % 2 == 0 { 'even' } else { 'odd' } println(s) // odd

If you're using if as an expression, for example, for returning its value or assigning it to a variable, the else branch is mandatory.

Therefore, there is no ternary operator (condition ? then : else) because ordinary if works fine in this role.

If unwrapping

To handle Result/Optional types, there is a special if:

struct User { id int name string } fn get_user(id int) !User { if id == 1 { return User{ id: 1 name: 'John' } } return error('user not found') } if user := get_user(0) { println(user) } else { // err is implicitly declared here and point // to the error returned by `get_user()` if any println(err) } // user not found

See Error handling for more information.

Match expression

os := 'windows' print('V is running on ') match os { 'darwin' { println('macOS') } 'linux' { println('Linux') } 'windows' { println('Windows') } else { println('unknown: ${os}') } }

A match statement is a shorter way to write a sequence of if-else statements. When a matching branch is found, the following statement block will be run. The else branch will be run when no other branches match.

number := 2 str := match number { 1 { 'one' } 2 { 'two' } else { 'many' } } println(str) // two

A match statement can also to be used as an if-else if-else alternative:

match true { 2 > 4 { println('if') } 3 == 4 { println('else if') } 2 == 2 { println('else if2') } else { println('else') } } // else if2

or as an unless alternative:

match false { 2 > 4 { println('if') } 3 == 4 { println('else if') } 2 == 2 { println('else if2') } else { println('else') } } // if

A match expression returns the value of the final expression from the matching branch.

enum Color { red blue green } fn is_red_or_blue(c Color) bool { return match c { .red, .blue { true } // comma can be used to test multiple values .green { false } } } println(is_red_or_blue(.red)) // true println(is_red_or_blue(.green)) // false

A match statement can also be used to branch on the variants of an enum by using the shorthand .variant_here syntax. An else branch is not allowed when all the branches are exhaustive.

enum Color { red blue green } c := Color.red match c { .red { println('red') } .blue { println('blue') } .green { println('green') } } // red

You can also use ranges as match patterns. If the value falls within the range of a branch, that branch will be executed.

c := `v` typ := match c { `0`...`9` { 'digit' } `A`...`Z` { 'uppercase' } `a`...`z` { 'lowercase' } else { 'other' } } println(typ) // lowercase

Note that the ranges use ... (three dots) rather than .. (two dots). This is because the range is inclusive of the last element, rather than exclusive (as .. ranges are). Using .. in a match branch will throw an error.

Constants can also be used in the range branch expressions.

const ( start = 1 end = 10 ) val := 2 num := match val { start...end { 1000 } else { 0 } } println(num) // 1000

match as an expression is not usable in for loop and if statements.

Conditions

# If expression

# If unwrapping

# Match expression

If expression

If unwrapping

Match expression