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This article is missing information about Nim's history, language design, tools, and paradigms. Please expand the article to include this information. Further details may exist on the talk page. (June 2019)
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The Nim crown logo
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| Paradigms | Multi-paradigm: compiled, concurrent, Procedural, Imperative, Functional, Object-oriented |
|---|---|
| Designed by | Andreas Rumpf |
| First appeared | 2008; 16 years ago (2008) |
| Stable release |
2.0.8[1] |
| Typing discipline | Static,[2] strong,[3] inferred, structural |
| Scope | Lexical |
| Platform | IA-32, x86-64 |
| OS | Cross-platform[4] |
| License | MIT[5][6] |
| Filename extensions | .nim, .nims, .nimble |
| Website | nim-lang |
| Influenced by | |
| Ada, Modula-3, Lisp, C++, Object Pascal, Python, Oberon | |
Nim is an imperative, general-purpose, multi-paradigm, statically typed, systems, compiled programming language[7] designed and developed by Andreas Rumpf. It is designed to be "efficient, expressive, and elegant",[8] supporting metaprogramming, functional, message passing,[5] procedural, and object-oriented programming styles by providing several features such as compile time code generation, algebraic data types, a foreign function interface (FFI) with C, C++, Objective-C, and JavaScript, and supporting compiling to those same languages.
Nim was created to be a language as fast as C, as expressive as Python, and as extensible as Lisp.
Nim is statically typed.[9] It supports compile-time metaprogramming features such as syntactic macros and term rewriting macros.[10] Term rewriting macros enable library implementations of common data structures, such as bignums and matrices, to be implemented efficiently, as if they were built-in language facilities.[11] Iterators are supported and can be used as first class entities,[10] as can functions, allowing for the use of functional programming methods. Object-oriented programming is supported by inheritance and multiple dispatch. Functions can be generic, they can be overloaded, and generics are further enhanced by Nim's support for type classes. Operator overloading is also supported.[10] Nim includes tunable automatic garbage collection based on deferred reference counting with cycle detection, which can also be turned off altogether.[12]
In 2014, Andrew Binstock (editor-in-chief of Dr. Dobb's Journal) said:
"[Nim] ... presents a most original design that straddles Pascal and Python and compiles to C code or JavaScript."[13]
As of April 2019[update], Nim compiles to C, C++, JavaScript, and Objective-C.
![[icon]](https://akarinohon.com/text/taketori.cgi/en.wikipedia.org/wiki/File:Wiki_letter_w_cropped.svg){kind=small} |
This section needs expansion. You can help by adding to it. (February 2018)
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| Version | Release date[14] |
|---|---|
| Old version, no longer maintained: 0.10.2 | 2014-12-29 |
| Old version, no longer maintained: 0.11.2 | 2015-05-04 |
| Old version, no longer maintained: 0.12.0 | 2015-10-27 |
| Old version, no longer maintained: 0.13.0 | 2016-01-18 |
| Old version, no longer maintained: 0.14.2 | 2016-06-09 |
| Old version, no longer maintained: 0.15.2 | 2016-10-23 |
| Old version, no longer maintained: 0.16.0 | 2017-01-08 |
| Old version, no longer maintained: 0.17.2 | 2017-09-07 |
| Old version, no longer maintained: 0.18.0 | 2018-03-01 |
| Old version, no longer maintained: 0.19.6 | 2019-05-13 |
| Old version, no longer maintained: 0.20.2 | 2019-06-17 |
| Old version, no longer maintained: 1.0.0 | 2019-09-23 |
| Old version, no longer maintained: 1.0.2 | 2019-10-23 |
| Old version, no longer maintained: 1.0.4 | 2019-11-26 |
| Old version, no longer maintained: 1.0.6 | 2020-01-24 |
| Old version, no longer maintained: 1.2.0 | 2020-04-03 |
| Old version, no longer maintained: 1.2.2 | 2020-06-17 |
| Old version, no longer maintained: 1.2.4 | 2020-06-27 |
| Old version, no longer maintained: 1.2.6 | 2020-07-30 |
| Old version, no longer maintained: 1.4.0 | 2020-10-16 |
| Current stable version: 1.4.4 | 2021-02-23 |
Legend: Old version Older version, still maintained Latest version Latest preview version Future release
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| For each 0.x branch, only the latest point release is listed |
Nim's initial development was started in 2005 by Andreas Rumpf. It was originally named Nimrod when the project was made public in 2008.[15]: 4–11 The first version of the Nim compiler was written in Pascal using the Free Pascal compiler.[16] In 2008, a version of the compiler written in Nim was released.[17] The compiler is free and open-source software, and is being developed by a community of volunteers working with Andreas Rumpf.[18] The language was officially renamed from NimrodtoNim with the release of version 0.10.2 in December 2014.[19] On September 23, 2019, version 1.0.0 of Nim was released, signifying the maturing of the language and its toolchain.
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This section needs expansion. You can help by adding to it. (February 2018)
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The syntax of Nim resembles that of Python.[20] Code blocks and nesting statements are identified through use of white-space, according to the offside-rule. Many keywords are identical to their Python equivalents, which are mostly English keywords, whereas other programming languages usually use punctuation. With the goal of improving upon its influence languages, even though Nim supports indentation-based syntax like Python, it introduced additional flexibility; one may break statements with a comma or binary operator to the next line. Additionally, Nim supports user-defined operators.
Nim is almost fully style-insensitive; two identifiers are considered equal if they only differ by capitalization and underscores, as long as the first characters are identical. Historically, Nim was fully case-insensitive (meaning that capitalization and underscores of the identifiers were fully ignored).[21]
Nim was influenced by specific characteristics of existing languages, including the following:
Nim supports Uniform Function Call Syntax (UFCS)[22] and identifier equality, which provides a large degree of flexibility in use.
For example, each of these lines does the same call, just with different syntax:
echo "hello world"
echo("hello world")
"hello world".echo()
"hello world".echo
"hello".echo(" world")
"hello".echo " world"
Except for the first letter, identifiers in Nim are compared in a case-insensitive manner, and underscores are ignored.
Example:
const useHttps = true
assert useHttps == useHttps
assert useHTTPS == useHttps
assert use_https == useHttps
The stropping feature allows to use any name for variables or functions, even when the names which a reserved words for keywords. An example of stropping is the ability to define a variable named if, without clashing with the keyword if. Nim's implementation of this is achieved via backticks, allowing any reserved word to be used as an identifier.[23]
type Type = object
`int`: int
let `object` = Type(`int`: 9)
assert `object` is Type
assert `object`.`int` == 9
var `var` = 42
let `let` = 8
assert `var` + `let` == 50
const `assert` = true
assert `assert`
The Nim compiler emits fast, optimized C code by default. It defers compiling-to-object code to an external C compiler[24] to leverage existing compiler optimization and portability. Many C compilers are supported, including Clang, Microsoft Visual C++ (MSVC), MinGW, and GNU Compiler Collection (GCC). The Nim compiler can also emit C++, Objective-C, and JavaScript code to allow easy interfacing with application programming interfaces (APIs) written in those languages;[7] developers can simply write in Nim, then compile to any supported language. This also allows writing applications for iOS and Android. There is also an unofficial LLVM backend, allowing use of the Nim compiler in a stand-alone way.[25]
The Nim compiler is self-hosting, meaning it is written in the Nim language.[26] The compiler supports cross-compiling, so it is able to compile software for any of the supported operating systems, no matter the development machine. This is useful for compiling applications for embedded systems, and for uncommon and obscure computer architectures.
By default, the Nim compiler creates a debug build.[27]
With the option -d:releasearelease build can be created, which is optimized for speed and contains fewer runtime checks.[27]
To disable all runtime checks, the option -d:danger can be used.[27]
Nim supports multiple memory management strategies, including the following:[28]
--gc:refc – Deferred reference counting based garbage collector with a simple Mark&Sweep backup GC to collect cycles. Heaps are thread-local. This is the default GC.--gc:orc – Reference counting with move semantic optimizations, a shared heap and a cycle collector based on "trial deletion".--gc:none – No automatic memory management.Many tools are bundled with the Nim install package, including:
Nimble is the standard package manager used by Nim to package Nim modules.[29] It was initially developed by Dominik Picheta, who is also a core Nim developer. Nimble has been included as Nim's official package manager since Oct 27, 2015, the v0.12.0 release.[30]
Nimble packages are defined by .nimble files, which contain information about the package version, author, license, description, dependencies, and more.[15]: 132 These files support a limited subset of the Nim syntax called NimScript, with the main limitation being the access to the FFI. These scripts allow changing of test procedure, or for custom tasks to be written.
The list of packages is stored in a JavaScript Object Notation (JSON) file which is freely accessible in the nim-lang/packages repository on GitHub. This JSON file provides Nimble with a mapping between the names of packages and their Git or Mercurial repository URLs.
Nimble comes with the Nim compiler. Thus, it is possible to test the Nimble environment by running:
nimble -v.
This command will reveal the version number, compiling date and time, and Git hash of nimble. Nimble uses the Git package, which must be available for Nimble to function properly. The Nimble command-line is used as an interface for installing, removing (uninstalling), and upgrading–patching module packages.[15]: 130–131
c2nim is a source-to-source compiler (transcompiler or transpiler) that helps to generate new bindings by translating ANSI C code to Nim code.[31] The output is human-readable Nim code that is meant to be optimized by hand after the translation process.
DrNim is a tool that combines the Nim compiler Frontend with the Z3 proof engine in order to allow verify and validate software written in Nim. Nim comes with DrNim source code included, but requires compilation using Koch, also bundled with Nim.
A maintenance script that is used to build Nim, and provide HTML documentation.
Nimgrep is a generic tool for manipulating text. It is used to search for regex, peg patterns, and contents of directories, and it can be used to replace tasks.
Nimsuggest is a tool that helps any source code editor query a .nim source file to obtain useful information like definition of symbols or suggestions for completions.
Niminst is a tool to generate an installer for a Nim program. It creates .msi installers for Windows via Inno Setup, and install and uninstall scripts for Linux, macOS, and Berkeley Software Distribution (BSD).
Nimpretty is a source code beautifier, used to format code according to the official Nim style guide.
Testament is an advanced automatic Unittests runner for Nim tests. Used in developing Nim, it offers process isolation tests, generates statistics about test cases, supports multiple targets and simulated Dry-Runs, has logging, can generate HTML reports, can skip tests from a file, and more.
Some notable tools not included in the Nim package include:
Choosenim was developed by Dominik Picheta, creator of the Nimble package manager, as a tool to enable installing and using multiple versions of the Nim compiler. It downloads any Nim stable or development compiler version from the command line, enabling easy switching between them.[32]
Nimfix is a tool to convert parts of old-style Nimrod code to Nim code.[33] As of 2019[update], it is in beta release.[34]
pas2nim is a tool to translate Object Pascal wrappers to Nim code.[35] pas2nim played an important role in Nim's timeline, as it was used to translate the original Pascal sources of the Nim compiler. Only what maps easily to Nim is supported; Free Pascal, Delphi-style classes are unsupported, as are some other hard-to-translate features. As of October 2020[update], development and maintenance on pas2nim is mostly stalled.
py2nim is a tool used to translate Python code into idiomatic Nim code.[36] As of 2020[update], its development is stalled.
Pure libraries are modules written in Nim only. They include no wrappers to access libraries written in other programming languages.
Impure libraries are modules of Nim code which depend on external libraries that are written in other programming languages such as C.
The Nim standard library includes modules for all basic tasks, including:[37]
A Nim program can use any library which can be used in a C, C++, or JavaScript program. Language bindings exist for many libraries, including GTK+, Qt QML,[38] wxWidgets,[39] Simple DirectMedia Layer (SDL) 2, Cairo, OpenGL, Windows API (WinAPI), zlib, libzip, OpenSSL, Vulkan[40] and cURL.[41] Nim works with PostgreSQL, MySQL, and SQLite databases. Nim can interface with the Lua,[42] Julia,[43] Rust,[44] C Sharp,[45] TypeScript,[46] and Python[47] programming languages.
The "Hello, World!" program in Nim:
echo("Hello, world!")
# Procedures can be called with no parentheses
echo "Hello, World!"
Another version of making a "Hello World" is...
stdout.write("Hello, world!\n")
Program to calculate the factorial of a positive integer using the iterative approach:
import strutils
var n = 0
try:
stdout.write "Input positive integer number: "
n = stdin.readline.parseInt
except ValueError:
raise newException(ValueError, "You must enter a positive number")
var fact = 1
for i in 2..n:
fact = fact * i
echo fact
Using the module math from Nim's standard library:
import math
echo fac(x)
A simple demonstration showing many of Nim's features.
func reverse(s: string): string =
for i in countdown(s.high, 0):
result.add s[i]
let str1 = "Reverse This!"
echo "Reversed: ", reverse(str1)
One of the more exotic features is the implicit result variable. Every procedure in Nim with a non-void return type has an implicit result variable that represents the value to be returned. In the for loop we see an invocation of countdown which is an iterator. If an iterator is omitted, the compiler will attempt to use an items iterator, if one is defined for the type specified.
Using GTK3 with gobject introspection through the gintro module:
import gintro/[gtk, glib, gobject, gio]
proc appActivate(app: Application) =
let window = newApplicationWindow(app)
window.title = "GTK3 application with gobject introspection"
window.defaultSize = (400, 400)
showAll(window)
proc main =
let app = newApplication("org.gtk.example")
connect(app, "activate", appActivate)
discard run(app)
main()
This code requires the gintro module to work, which is not part of the standard library. To install the module gintro and many others you can use the tool nimble, which comes as part of nim. To install the gintro module with nimble you do the following:
nimble install gintro
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This is an example of metaprogramming in Nim using its template facilities.
template genType(name, fieldname: untyped, fieldtype: typedesc) =
type
name = object
fieldname: fieldtype
genType(Test, foo, int)
var x = Test(foo: 4566)
echo(x.foo) # 4566
The genType is invoked at compile-time and a Test type is created.
Nim supports both constrained and unconstrained generic programming. Generics may be used in procedures, templates and macros. They are defined after the proc's name in square brackets, as seen below.
proc addThese[T](a, b: T): T =
a + b
echo addThese(1, 2) # 3 (of int type)
echo addThese(uint8 1, uint8 2) # 3 (of uint8 type)
InaddThese, T is the generic type, the compiler will accept any values for this function as long as both parameters and the return value are of the same type.
One can further clarify which types the procedure will accept by specifying a type class.[48]
proc addTheseNumbers[T: SomeNumber](a, b: T): T =
a + b
addTheseNumberswill then only work for types contained in the SomeNumbersum type.
Macros can literally rewrite parts of the code before it's compiled. Nim macros are powerful and can do many operations on the abstract syntax tree.
Here's a simple example, that creates a macro called twice:
import macros
macro twice(arg: untyped): untyped =
result = quote do:
`arg`
`arg`
twice echo "Hello world!"
The twice macro in this example takes the echo statement in the form of an abstract syntax tree as input. In this example we decided to return this syntax tree without any manipulations applied to it. But we do it twice, hence the name of the macro. The end result is that the code gets rewritten by the macro to look like the following code at compile time:
echo "Hello world!"
echo "Hello world!"
Nim's FFI is used to call functions written in the other programming languages that it can compile to. This means that libraries written in C, C++, Objective-C, and JavaScript can be used in the Nim source code. One should be aware that both JavaScript and C, C++, or Objective-C libraries cannot be combined in the same program, as they are not as compatible with JavaScript as they are with each other. Both C++ and Objective-C are based on and compatible with C, but JavaScript is incompatible, as a dynamic, client-side web-based language.[15]: 226 </ref>
The following program shows the ease with which external C code can be used directly in Nim.
proc printf(formatstr: cstring) {.header: "<stdio.h>", varargs.}
printf("%s %d\n", "foo", 5)
In this code the printf function is imported into Nim and then used.
Basic example using 'console.log' directly for the JavaScript compilation target:
proc log(args: any) {.importjs: "console.log(@)", varargs.}
log(42, "z", true, 3.14)
The JavaScript code produced by the Nim compiler can be executed with Node.js or a web browser.
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To activate threading support in Nim, a program should be compiled with --threads:on command line argument. Each thread has a separate garbage collected heap and sharing of memory is restricted, which helps with efficiency and stops race conditions by the threads.
import locks
var
thr: array[0..4, Thread[tuple[a,b: int]]]
L: Lock
proc threadFunc(interval: tuple[a,b: int]) {.thread.} =
for i in interval.a..interval.b:
acquire(L) # lock stdout
echo i
release(L)
initLock(L)
for i in 0..high(thr):
createThread(thr[i], threadFunc, (i*10, i*10+5))
joinThreads(thr)
Nim also has a channels module that simplifies passing data between threads.
import os
type
CalculationTask = object
id*: int
data*: int
CalculationResult = object
id*: int
result*: int
var task_queue: Channel[CalculationTask]
var result_queue: Channel[CalculationResult]
proc workerFunc() {.thread.} =
result_queue.open()
while true:
var task = task_queue.recv()
result_queue.send(CalculationResult(id: task.id, result: task.data * 2))
var workerThread: Thread[void]
createThread(workerThread, workerFunc)
task_queue.open()
task_queue.send(CalculationTask(id: 1, data: 13))
task_queue.send(CalculationTask(id: 2, data: 37))
while true:
echo "got result: ", repr(result_queue.recv())
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Nim supports asynchronous IO via the asyncdispatch module, which adds async/await syntax via the macro system. An example of an asynchronous http server:
import asynchttpserver, asyncdispatch
var server = newAsyncHttpServer()
proc cb(req: Request) {.async.} =
await req.respond(Http200, "Hello World")
waitFor server.serve(Port(8080), cb)
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Nim has an active community on the self-hosted, self-developed official forum.[49] Further, the project uses a Git repository, bug tracker, and wiki hosted by GitHub, where the community engages with the language.[50]
The first Nim conference, NimConf, took place on June 20, 2020. It was held digitally due to COVID-19, with an open call for contributor talks in the form of YouTube videos.[51] The conference began with language overviews by Nim developers Andreas Rumpf and Dominik Picheta. Presentation topics included talks about Nim web frameworks, mobile development, Internet of things (IoT) devices, and game development, including a talk about writing Nim for Game Boy Advance.[52] NimConf 2020 is available as a YouTube playlist.[53]
In addition to official conferences, Nim has been featured at various other conventions. A presentation on Nim was given at the O'Reilly Open Source Convention (OSCON) in 2015.[54][55][56] Four speakers represented Nim at Free and Open source Software Developers' European Meeting (FOSDEM) 2020, including the creator of the language, Andreas Rumpf.[57]
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