V (programming language): Difference between revisions

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The new language was created as a result of frustration with existing languages being used for personal projects.{{sfn|Chakraborty|Haldar|2023}} It was originally intended for personal use, but after being mentioned publicly and increasing interest, it was decided to make it public. V was initially created to develop a desktop messaging client named Volt.<ref name="hackaday"/> On public release, the compiler was written in V, and could [[Self-hosting (compilers)|compile itself]].{{Sfn|Rao|2021}}{{sfn|Chakraborty|Haldar|2023}} Key design goals in creating V were being easy to learn and use, higher readability, fast compiling, increased safety, efficient development, [[Cross-platform software|cross-platform]] usability, improved [[C (programming language)|C]] [[interoperability]], better [[Error detection and correction|error handling]], modern features, and more maintainable software.<ref name="MUO"/><ref name="analyticsindiamag"/><ref name="nasufi"/><ref>{{cite web |title=V language: simple like Go, small binary like Rust|url=https://techracho.bpsinc.jp/hachi8833/2021_03_09/89457/ |website=TechRacho |access-date=3 March 2021}}</ref>

V is released and developed through [[GitHub]],<ref>{{cite web |url=https://ossinsight.io/analyze/vlang/v#overview |title=GitHub Programming Languages (repository details) |via=[[Open-source software|OSS]] Insight using [[TiDB]]}}</ref><ref name="hackaday"/> and maintained by developers and contributors internationally.{{Sfn|Rao|2021}} It is among the languages that have been listed on the [[TIOBE index]].<ref>{{cite web |title=TIOBE Index |url=https://www.tiobe.com/tiobe-index |publisher=[[TIOBE index|TIOBE]]|website=tiobe |archive-url=https://web.archive.org/web/20250411043213/https://www.tiobe.com/tiobe-index/|archive-date=11 April 2025|access-date=11 April 2025}}</ref>

[[File:Veasel.svg|thumb|Veasel is the official mascot of the V programming language<ref>{{cite web |url=https://github.com/vlang/v-mascot/ |title=V's official mascot |website=GitHub |access-date=8 November 2023}}</ref>]]

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== Syntax ==

=== Hello world ===

The [["Hello, World!" program]] in V:<ref name="MUO"/><ref name=":0">{{Cite web |title=V Documentation |url=https://docs.vlang.io/ |access-date=2025-08-25 |website=docs.vlang.io}} {{Free-content attribution|title = V Documentation| license statement URL =https://github.com/vlang/v?tab=MIT-1-ov-file| license=The MIT License|this = yes}}</ref>

The [["Hello, World!" program]] in V:<ref name="MUO"/>

<syntaxhighlight lang="v">

fn main() {

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=== Variables ===

Variables are immutable by default and are defined using {{code|1=:=}} and a value. Use the {{code|mut}} [[reserved word]] (keyword) to make them mutable. Mutable variables can be assigned to using {{code|1==}}:{{sfn|Rao|2021|pp=28-40}}<ref name=":0" />

<syntaxhighlight lang="V">

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</syntaxhighlight>

Redeclaring a variable, whether in an inner scope or in the same scope, is not allowed:{{sfn|Rao|2021|pp=28-40}}<ref name=":0" />

<syntaxhighlight lang="V">

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=== Structs ===

Struct example:<ref name="Knott"/><ref name="section"/><ref name=":0" />

<syntaxhighlight lang="Vv">

struct PlaceFoo {

a number int

name string

b int

score f32

}

// Struct fields can be initialized by name

mut p := Place {

var1 := Foo {

a: 15

number: 21

b: 25

name: "baz"

score: 2.5

}

println(p.a) // A dot is used to access struct fields

// or by position

// Alternative literal syntax can be used

pvar2 := PlaceFoo{1550, 25"taz", 3.14}

assert p.a == 15

</syntaxhighlight>

=== Heap structs ===

Structs are allocated on the stack by default. The {{code|&}} prefix can be used, for getting a reference to it and allocating on the heap instead: {{sfn|Rao|2021}}

By default, structs are allocated on the [[Stack_memory|stack]]. When structs are referenced by using the prefix {{code|1=&}} or have the {{code|1=[heap]}} attribute, they are allocated on the [[Heap-based_memory_allocation|heap]] instead:{{sfn|Rao|2021}}<ref name=":0" />

<syntaxhighlight lang="Vv">

struct PlaceFoo {

a int

b number int

}

@[heap]

p := &Place{30, 30}

struct UserBaz {

// References use the same syntax to access fields

number f32

println(p.a)

}

// Structs that are referenced are heap allocated

var1 := &Foo{2}

// Baz is always heap allocated because of its [heap] attribute

var2 := Baz{4.5}

</syntaxhighlight>

=== Methods ===

[[Method (computer programming)|Methods]] in V are functions defined with a receiver [[Parameter (computer programming)|argument]]. The receiver appears in its own argument list between the {{code|1=fn}} keyword and the method name. Methods must be in the same [[Modular programming|module]] as the receiver type.

The is_registeredenrolled_status method (below) has a receiver of type User{{code|1=Client}} named u{{code|1=x}}. The convention is not to use receiver names like self or this, but preferably a short name. For example:<ref name="Knott"/><ref name="nasufi"/><ref name=":0" /><syntaxhighlight lang="v">

struct Client {

enrolled bool

<syntaxhighlight lang="V">

struct User {

age int

}

fn (ux UserClient) is_registeredenrolled_status() bool {

return x.enrolled

return u.age > 16

}

println(Client{enrolled: true}.enrolled_status()) // true

user := User{

println(Client{enrolled: false}.enrolled_status()) // false

age: 10

}

println(user.is_registered()) // "false"

user2 := User{

age: 20

}

println(user2.is_registered()) // "true"

</syntaxhighlight>

=== Error handling ===

OptionalResult types aremay forrepresent typesan whicherror mayreturned representfrom nonea function. Result types mayare representdeclared anby errorprepending returned{{code|!}}: from a function.{{code|!Type}}

OptionOptional types are declared bymay prependingrepresent {{code|?none}}. toOption thetypes type name:prepend {{code|?Type}}. Resultto typesthe usetype {{code|!}}name: {{code|!?Type}}.<ref name="Knott"/><ref name="section"/>{{Sfn|Tsoukalos|2022}}<ref name=":0" />

<syntaxhighlight lang="V">

fn something(t string) !string {

if t == "foo" { return "foo" }

return error("invalid string")

}

x := something("foo") or { "default" } // x will be "foo"

y := something("carbaz") or { "default" } // y will be "default"

z := something("carbaz") or { panic("{err}") } // z will exit with an error "invalid string" and a traceback

println(x)