For each 0.x branch, only the latest point release is listed. For later branches, the first and the latest point release is listed.
Andreas Rumpf is the designer and original implementer of Nim. He received a diploma in computer science from the University of Kaiserslautern-Landau, Germany. His research interests include hard realtime systems, embedded systems, compiler construction and artificial intelligence. [20]
Nim's original website design by Dominik Picheta and Hugo Locurcio. Joseph Wecker created the Nim's logo.
The Nim programming language is a concise, fast programming language that compiles to C, C++ and JavaScript. Nim's initial development was started in 2005 by Andreas Rumpf. It was originally named Nimrod when the project was made public in 2008.[21]: 4–11
The first version of the Nim compiler was written in Pascal using the Free Pascal compiler.[22] In 2008, a version of the compiler written in Nim was released.[23] The compiler is free and open-source software, and is being developed by a community of volunteers working with Andreas Rumpf.[24] The language was officially renamed from Nimrod to Nim with the release of version 0.10.2 in December 2014.[25] On September 23, 2019, version 1.0 of Nim was released, signifying the maturing of the language and its toolchain. On August 1st, 2023, version 2.0 of Nim was released, signifying the completion, stabilization of, and switch to the ARC/ORC memory model.[26]
Language design
Syntax
The syntax of Nim resembles that of Python.[27] Code blocks and nesting statements are identified through use of whitespace, 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. For example, a single statement may span multiple lines if a comma or binary operator is at the end of each line. Nim also supports user-defined operators.
Unlike Python, Nim implements (native) static typing. Nim's type system allows for easy type conversion, casting, and provides syntax for generic programming. Nim notably provides type classes which can stand in for multiple types, and provides several such type classes 'out of the box'. Type classes allow working with several types as if they were a single type. For example:
openarray – Represents arrays of different sizes, sequences, and strings
SomeSignedInt – Represents all the signed integer types
SomeInteger – Represents all the Integer types, signed or not
SomeOrdinal – Represents all the basic countable and ordered types, except of non integer number
This code sample demonstrates the use of typeclasses in Nim]
# Let's declare a function that takes any type of number and displays its double# In Nim functions with side effect are called "proc"proctimesTwo(i:SomeNumber)=echoi*2
# Let's write another function that takes any ordinal type, and returns# the double of the input in its original type, if it is a number;# or returns the input itself otherwise.# We use a generic Type(T), and precise that it can only be an OrdinalfunctwiceIfIsNumber[T:SomeOrdinal](i:T):T=whenTisSomeNumber:# A `when` is an `if` evaluated during compile timeresult=i*2# You can also write `return i * 2`else:# If the Ordinal is not a number it is converted to int,# multiplied by two, and reconverted to its based typeresult=(i.int*2).T
echotwiceIfIsNumber(67)# Passes an int to the function
echo twiceIfIsNumber(67u8) # Passes an uint8echotwiceIfIsNumber(true)# Passes a bool (Which is also an Ordinal)
Influence
According to the language creator, Nim was conceived to combine the best parts of Ada typing system, Python flexibility, and powerful Lisp macro system.[28]
Nim was influenced by specific characteristics of existing languages, including the following:
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. This is to enable a mixture of styles across libraries: one user can write a library using snake_case as a convention, and it can be used by a different user in a camelCase style without issue.[30]
The stropping feature allows the use of any name for variables or functions, even when the names are 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.[31]
The Nim compiler emits fast, optimized C code by default. It defers compiling-to-object code to an external C compiler[32] 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;[9] 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.[18]
The Nim compiler is self-hosting, meaning it is written in the Nim language.[33] 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.[citation needed]
Compiler options
By default, the Nim compiler creates a debug build.[34]
With the option -d:release a release build can be created, which is optimized for speed and contains fewer runtime checks.[34]
With the option -d:danger all runtime checks can be disabled, if maximum speed is desired.[34]
Memory management
Nim supports multiple memory management strategies, including the following:[35]
--mm:arc – Automatic reference counting (ARC) with move semantics optimizations, offers a shared heap. It offers fully deterministic performance for hard realtime systems.[36] Reference cycles may cause memory leaks: these may be dealt with by manually annotating {.acyclic.} pragmas or by using --mm:orc.
--mm:orc – Same as --mm:arc but adds a cycle collector (the "O") based on "trial deletion".[37] The cycle collector only analyzes types if they are potentially cyclic.
--mm:refc – Standard deferred reference counting based garbage collector with a simple mark-and-sweep backup GC in order to collect cycles. Heaps are thread-local.
--mm:go – Go's garbage collector, useful for interoperability with Go. Offers a shared heap.
--mm:none – No memory management strategy nor a garbage collector. Allocated memory is simply never freed, unless manually freed by the developer's code.
Many tools are bundled with the Nim install package, including:
Nimble
Nimble is the standard package manager used by Nim to package Nim modules.[39] 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.[40]
Nimble packages are defined by .nimble files, which contain information about the package version, author, license, description, dependencies, and more.[21]: 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.[21]: 130–131
c2nim
c2nim is a source-to-source compiler (transcompiler or transpiler) meant to be used on C/C++ headers to help generate new Nim bindings.[41] The output is human-readable Nim code that is meant to be edited by hand after the translation process.
koch
koch is a maintenance script that is used to build Nim, and provide HTML documentation.[42]
nimgrep
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. It is included to assist with searching Nim's style-insensitive identifiers.[43]
nimsuggest
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.[44]
niminst
niminst is a tool to generate an installer for a Nim program.[45]
It creates .msi installers for Windows via Inno Setup, and install and uninstall scripts for Linux, macOS, and Berkeley Software Distribution (BSD).
nimpretty
nimpretty is a source code beautifier, used to format code according to the official Nim style guide.[46]
Testament
Testament is an advanced automatic unit tests 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.
Other notable tools
Some notable tools not included in the Nim distribution include:
choosenim
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.[47]
nimpy
nimpy is a library that enables convenient Python integration in Nim programs.[48]
pixie
pixie is a feature-rich 2D graphics library, similar to Cairo or the Skia. It uses SIMD acceleration to speed-up image manipulation drastically. It supports many image formats, blending, masking, blurring, and can be combined with the boxy library to do hardware accelerated rendering.
nimterop
nimterop is a tool focused on automating the creation of C/C++ wrappers needed for Nim's foreign function interface.[49]
Libraries
Pure/impure libraries
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.
Standard library
The Nim standard library includes modules for all basic tasks, including:[50]
Program to calculate the factorial of a positive integer using the iterative approach, showcasing try/catch error handling and for loops:
importstd/strutilsvarn=0try:stdout.write"Input positive integer number: "n=stdin.readline.parseIntexceptValueError:raisenewException(ValueError,"You must enter a positive number")varfact=1foriin2..n:fact=fact*iechofact
Using the module math from Nim's standard library:
importstd/mathechofac(x)
Reversing a string
A simple demonstration showing the implicit result variable and the use of iterators.
One of Nim's 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.
Graphical user interface
Using GTK 3 with GObject introspection through the gintro module:
importgintro/[gtk,glib,gobject,gio]procappActivate(app:Application)=letwindow=newApplicationWindow(app)window.title="GTK3 application with gobject introspection"window.defaultSize=(400,400)showAll(window)procmain=letapp=newApplication("org.gtk.example")connect(app,"activate",appActivate)discardrun(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
Programming paradigms
Functional programming
Functional programming is supported in Nim through first-class functions and code without side effects via the noSideEffect pragma or the func keyword.[71] Nim will perform side effect analysis and raise compiling errors for code that does not obey the contract of producing no side effects when compiled with the experimental feature strictFuncs, planned to become the default in later versions.[72]
Nim supports first-class functions by allowing functions to be stored in variables or passed anonymously as parameters to be invoked by other functions.[73] The std/sugar module provides syntactic sugar for anonymous functions in type declarations and instantiation.
importstd/[sequtils,sugar]letpowersOfTwo=@[1,2,4,8,16,32,64,128,256]procfilter[T](s:openArray[T],pred:T->bool):seq[T]=result=newSeq[T]()foriin0..<s.len:ifpred(s[i]):result.add(s[i])echopowersOfTwo.filter(proc(x:int):bool=x>32)# syntactic sugar for the above, provided as a macro from std/sugarechopowersOfTwo.filter(x=>x>32)procgreaterThan32(x:int):bool=x>32echopowersOfTwo.filter(greaterThan32)
Side effects
Side effects of functions annotated with the noSideEffect pragma are checked, and the compiler will refuse to compile functions failing to meet those. Side effects in Nim include mutation, global state access or modification, asynchronous code, threaded code, and IO. Mutation of parameters may occur for functions taking parameters of var or ref type: this is expected to fail to compile with the currently-experimental strictFuncs in the future.[74] The func keyword introduces a shortcut for a noSideEffect pragma.[75]
funcbinarySearch[T](a:openArray[T];elem:T):int
# is short for...
procbinarySearch[T](a:openArray[T];elem:T):int {.noSideEffect.}
{.experimental: "strictFuncs".}
typeNode=refobjectle,ri:Nodedata:stringfunclen(n:Node):int=
# valid: len does not have side effects
varit=nwhileit!=nil:incresultit=it.rifuncmut(n:Node)=letm=n# is the statement that connected the mutation to the parameterm.data="yeah"# the mutation is here# Error: 'mut' can have side effects# an object reachable from 'n' is potentially mutated
importstd/[sequtils,sugar]letnumbers=@[1,2,3,4,5,6,7,8,7,6,5,4,3,2,1]# a and b are special identifiers in the foldr macroechonumbers.filter(x=>x>3).deduplicate.foldr(a+b)# 30
Despite being primarily an imperative and functional language, Nim supports various features for enabling object-oriented paradigms.[79][80]
Subtyping and inheritance
Nim supports limited inheritance by use of ref objects and the of keyword.[80] To enable inheritance, any initial ("root") object must inherit from RootObj. Inheritance is of limited use within idiomatic Nim code: with the notable exception of Exceptions.[81]
Subtyping relations can also be queried with the of keyword.[80]
Method calls and encapsulation
Nim's uniform function call syntax enables calling ordinary functions with syntax similar to method call invocations in other programming languages. This is functional for "getters": and Nim also provides syntax for the creation of such "setters" as well. Objects may be made public on a per-field basis, providing for encapsulation.
typeSocket*=refobjecthost:int# private, lacks export marker# getter of host addressprochost*(s:Socket):int=s.host# setter of host addressproc`host=`*(s:varSocket,value:int)=s.host=valuevars:Socketnewsasserts.host==0# same as host(s), s.host()s.host=34# same as `host=`(s, 34)
Dynamic dispatch
Static dispatch is preferred, more performant, and standard even among method-looking routines.[80] Nonetheless, if dynamic dispatch is so desired, Nim provides the method keyword for enabling dynamic dispatch on reference types.
importstd/strformattypePerson=refobjectofRootObjname:stringStudent=refobjectofPersonTeacher=refobjectofPersonmethodintroduce(a:Person)=raisenewException(CatchableError,"Method without implementation override")methodintroduce(a:Student)=echo&"I am a student named {a.name}!"methodintroduce(a:Teacher)=echo&"I am a teacher named {a.name}!"letpeople:seq[Person]=@[Teacher(name:"Alice"),Student(name:"Bob")]forpersoninpeople:person.introduce()
Metaprogramming
Templates
Nim supports simple substitution on the abstract syntax tree via its templates.
The genType is invoked at compile-time and a Test type is created.
Generics
Nim supports both constrained and unconstrained generic programming.
Generics may be used in procedures, templates and macros. Unconstrained generic identifiers (T in this example) are defined after the routine's name in square brackets. Constrained generics can be placed on generic identifiers, or directly on parameters.
procaddThese[T](a,b:T):T=a+bechoaddThese(1,2)# 3 (of int type)echoaddThese(uint81,uint82)# 3 (of uint8 type)# we don't want to risk subtracting unsigned numbers!procsubtractThese[T:SomeSignedInt|float](a,b:T):T=a-bechosubtractThese(1,2)# -1 (of int type)importstd/sequtils# constrained generics can also be directly on the parametersproccompareThese[T](a,b:string|seq[T]):bool=for(i,j)inzip(a,b):ifi!=j:returnfalse
One can further clarify which types the procedure will accept by specifying a type class (in the example above, SomeSignedInt).[82]
Macros
Macros can rewrite parts of the code at compile-time. Nim macros are powerful and can operate on the abstract syntax tree before or after semantic checking.[83]
Here's a simple example that creates a macro to call code twice:
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 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!"
Foreign function interface (FFI)
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.[21]: 226
The following program shows the ease with which external C code can be used directly in Nim.
The JavaScript code produced by the Nim compiler can be executed with Node.js or a web browser.
Parallelism
This section needs expansion. You can help by adding to it. (June 2019)
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.
This section needs expansion. You can help by adding to it. (June 2019)
Asynchronous IO is supported either via the asyncdispatch module in the standard library or the external chronos library.[84] Both libraries add async/await syntax via the macro system, without need for special language support. An example of an asynchronous HTTP server:
importstd/[asynchttpserver,asyncdispatch]# chronos could also be alternatively used in place of asyncdispatch,# with no other changes.varserver=newAsyncHttpServer()proccb(req:Request){.async.}=awaitreq.respond(Http200,"Hello World")waitForserver.serve(Port(8080),cb)
Community
Online
Nim has an active community on the self-hosted, self-developed official forum.[85] Further, the project uses a Git repository, bug tracker, RFC tracker, and wiki hosted by GitHub, where the community engages with the language.[86] There are also official online chat rooms, bridged between IRC, Matrix, Discord, Gitter, and Telegram.[87]
![[icon]](File:Wiki_letter_w_cropped.svg){kind=small}
