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Overview for mimium

Documentation is under preparation! Seeking for people who support documentations and translations.

mimium(MInimal-Musical-medIUM) is a domain specific programming language for describing/generating sound and music.

With this language, you can write a low-level audio processing with an easy expression and high-performance powered by LLVM.

fn lpf(input:float,fb:float){    
    return (1-fb)*input + fb*self

A special keyword self can be used in function, which is a last return value of the function. This enables an easy and clean expression of feedback connection of signal chain, inspired by Faust.

you can also write a note-level processing by using a temporal recursion, inspired by Extempore.

fn noteloop()->void{
    freq =  (freq+1200)%4000
    noteloop()@(now + 48000)

Calling function with @ specifies the time when the function will be executed. An event scheduling for this mechanism is driven by a clock from an audio driver thus have a sample-accuracy.

1 - Users Guide

1.1 - Getting Started

Let’s start your mimium experiences


Currently, mimium can be used on the following environments.

  • macOS (x86)
  • Linux(tested on Ubuntu, uses ALSA as backend)
  • Windows 10

Getting started with an extension for Visual Studio Code

The easiest way to get started is to use Visual Studio Code, a free text editor/IDE.

  1. download and install Visual Studio Code from the official website.
  2. Start Visual Studio Code, and open the Extensions menu (Cmd+Shift+X).
  3. search for “mimium” in the search field and install it.
  4. Create a file with the name of `hello.mmm’, copy the following code snippet, save it, and open it again in Visual Studio Code.
  5. A pop-up window will appear asking you to install the latest version of the mimium binary.
  6. Cmd+Shift+P to open the command palette, search for “mimium”, and execute the command “Run currently opening file” to run the file currently open in the editor from the terminal.
  7. If you want to stop the sound, press Ctrl+C in the terminal.
// hello.mmm
fn dsp(){
  output = sin(now*440*2*3.141595/48000)
  return (output,output)

Other ways to install

You can download latest binaries from GitHub Release. Copy bin/mimium to appropariate path (for example, /usr/loca/bin on macOS/Linux).

On macOS/Linux, you can easily install mimium by using Homebrew/Linuxbrew1.

brew install mimium-org/mimium/mimium

for more detailed information such as building from source, check Installation page.

Run the command

You can run mimium by running mimium command. If the binary is correctly installed, you can see the help menu with the following command.

mimium --help

Make text file with the name of hello.mmm on current working directory and paste the code snippet above.

Then, type the following command to run the file. (Take care the volume of speakers.) You will hear the sine wave sound of 440Hz.

mimium hello.mmm


You can read further explanation such as a grammer of the language and available functions on Making Sound page.

  1. Currently, we can not provide a binary package for macOS 11.0 thus it tries to build from the source. Installing Xcode and some additional software are required. ↩︎

1.1.1 - Examples

The entry point for the beginners of mimium - step by step example.
  1. dsp
  2. “self” example
  3. a simple effect
  4. composition
  5. sol-fa
  6. rhythm pattern

Example: sol-fa

In the example below, the system’s audio driver sample rate is 48000 Hz, and it will play sol-fa sounds every second.

notes = [440,495,260.7,293.3,330,347.7,391.1]
index = 0
fn updateIndex(){
  index = (index+1)%7
fn dsp(){
 vol = 0.2
 octave = 1
 sec = now/48000
 freq = notes[index]
 out = vol * sin(octave*freq*3.14*2*sec)
 return (0,out)

Point 1: Arrays.

notes = [440,495,260.7,293.3,330,347.7,391.1] // 1st line

In mimium, you can define an array. Arrays are defined using []. The beginning of the index is 0. In this example, the first line of the array that creates the sol-fa sounds note contains the frequencies of the A-B-C-D-E-F-G notes, which are used in subsequent processing.

  • A: 440Hz
  • B: 495Hz
  • C: 260.7Hz
  • D: 293.3Hz
  • E: 330Hz
  • F: 347.7Hz
  • G: 391.1Hz

The way to use arrays is to use array_name[index], as in line 12. freq = notes[index] // line 12.

Point 2: Temporal Recursion

// Lines 3~7
fn updateIndex(){
  index = (index+1)%7

V0.3.0 does not adopt the for-loop statement that most languages have. However, you can describe repetitive executions of the function by using a design pattern called temporal recursion as shown in lines 3~6. In the sol-fa example, after executing updateIndex() at 48000 samples in line 7, the now and @ keywords are used together in the function to execute updateIndex() at 48000 samples from the current time (line 5).

Point 3: Using the now and @ keywords together

updateIndex()@(now+48000) // line 5

In mimium, the current number of samples can be retrieved using now. Users should note that in the v0.3.0 current specification, the now keyword does not represent real-time. The unit is sample1.

Also, mimium has a @ keyword, which means “execute the function before @ when the number of samples is the number of values resulting from the calculation of the expression after @.

The @ time indicates the absolute time since the audio driver was started, so if you write updateIndex()@48000 as in line 7, it will always execute updateIndex() once 48000 samples after it was started. In the fifth line of the example, by connecting now and 48000 with the + keyword, we can determine the sample point in time from the current time, and by using @, we can execute the function at that sample point.

Point 4: Octave

// Lines 8~15
fn dsp(){
 vol = 0.2
 octave = 1
 sec = now/48000
 freq = notes[index]
 out = vol  *sin(octave*freq*3.14*2*sec)
 return (0,out)

In the musical scale, there is a relationship between doubling the frequency (Hz) and going up an octave, and conversely, halving the frequency and going down an octave. In lines 8 to 15 of the example, the value is fixed at octave = 1, so it plays a sol-fa sounds from 260.7Hz to 495Hz, but if you change this value to 2, for example, you can express a scale that goes up an octave.

  1. mimium currently does not provide a way to get a samplerate of the audio driver. In the future, this will be realized by introducing environment-variables(runtime-defined variables). ↩︎

1.1.2 - Making Sound

Here you will learn how to make the basic sound using the mimium.

Documentation is under preparation! We are seeking for people who support documentations and translations.

Making 440Hz Sine wave sound

  1. Prepare a MMM file(e.g. sin.mmm). If you haven’t installed mimium at this point, see Installation.
  2. Write the following code and saving the file.
fn dsp(time){
    return sin(now*440*3.14*2/48000)

Otherwise you can write one-liner code snippets.

dsp = |t|{ sin(now*440*3.14*2/48000) }
  1. Using your command line tool (e.g. bash), run the previous code.
$ mimium sin.mmm

1.1.3 - Installation

Install mimium to your computer

Documentation is under preparation! We are seeking for people who support documentations and translations.

Install through homebrew

For easier installation, using Homebrew, a package manager tool for macOS and Linux is recommended.

If you have not installed homebrew, open terminal app and copy & paste next line and hit Enter key.

/bin/bash -c "$(curl -fsSL"

If you got homebrew, you can install mimium by typing

brew install mimium-org/mimium/mimium

That’s it! You can check if you have successfully installed or not by

mimium --version # will return mimium version:x.x.x

Install manually

You can download built binary from GitHub Release Page. is for macOS, is for Linux and is for Windows.

After finished downloading and extracting zip files, copy mimium inside bin folder into /usr/local/bin, all files inside lib into /usr/local/lib. On GNU/Linux, note that the directory /usr/local/lib is not in library path by default, so don’t forget to add this directory to /etc/ and run ldconfig as root.

Build from source manually

mimium compiler & runtime are written in C++ thus you need C++ compiler. Xcode clang on macOS(you can install by just typing xcode-select --install) and GCC >= 9 is recommended on Linux.

You also need several libraries and build tools below.

on macOS, git and cmake are installed if you got xcode clang.

Also the codes depends on RtAudio(a cross-platform audio driver library) library but it will be downloaded & built automatically by cmake at a configure step.

You can of course install these dependencies via brew, or apt-get.

Get a source code from GitHub repository

git clone
cd mimium
# 'master' branch is a stable version. You can get the development version from 'dev' branch. 
git checkout master 

Configure CMake

mkdir build && cd build
cmake .. 

At this step, CMake will download and build RtAudio Library. You can pass generic options for CMake configuration option, for example,

  • -DCMAKE_INSTALL_PREFIX=/your/directory specifies installation path.
  • -DCMAKE_BUILD_TYPE=Debug specifies build optimization level. You can choose from ‘Debug’, ‘Release’, ‘MinSizeRel’ , ‘RelWithDebinfo’
  • -DCMAKE_CXX_COMPILER=/path/to/compiler specifies C++ compiler.
  • -DBUILD_SHARED_LIBS=ON Build libraries as dynamic-link library.(Not well tested on Linux and Windows)。
  • -DBUILD_TEST=ON Include tests to build targets.
  • -DENABLE_COVERAGE=ON Enable compiler option to calculate code-cvoerage using GCov.


cmake --build build -j

-j option controls maximum number of parallel CPU threads usage(e.g. -j8 means up to 8 threads). -j with no number means possible maximum number on your platform.


cmake --build build target=install


#(on build folder)
cmake --build build --target uninstall

This uninstall target uses information on build/install_manifest.txt generated by CMake at installation steps. If you fail to remove files, check this file and try build , installation and uninstall steps sequentialy again.

Syntax Highlight for Visual Studio Code

Currently, we have a syntax highlight for Visual Studio Code, a cross platform text editor/development environment.

You can get by searching mimium-language on an extension panel on VS Code or you can get from the link below.

1.2 - Language Specification

1.2.1 - Grammar Definition

This page is about the definition of mimium grammer.

This page is about the rule of mimium grammer.

Comment out

As in C++ and JavaScript, anything to the right of // in a line is treated as a comment. You can also comment out multiple lines at once by enclosing them as /* */.

Variable declaration and assignment

In mimium, when a value is assigned with the = operator, a new variable is created if the variable with the specified name does not exist yet. There is no need to use keywords such as ``let’’ when declaring variables.

``rust mynumber = 1000 The variables are all modifiable (mutable).

All variables are mutable. All variables are mutable, i.e., you can assign new values to variables that have already been declared.

mynumber = 1000 // variable is declared, and 1000 is assigned
mynumber = 2000 // 2000 is newly assigned to mynumber


Type is a concept to distinguish between variables and other data, such as numbers and strings, depending on their purpose. mimium is a statically typed language, which means that all types are determined at compile time (before the actual sound is made).

Statically typed languages generally have an advantage in terms of execution speed over languages that check types during execution. On the other hand, there is a disadvantage of manual type specification, which tends to lead to long descriptions. mimium has a feature called Type Inference, which allows you to omit type annotations if the type can be automatically determined from the context, thus keeping your code concise.

There are two types: primitive types, which are the smallest unit that cannot be further decomposed, and aggregate types, which are made by combining multiple types.

Explicit annotation of types is possible at the time of variable declaration and function declaration. In the parameters of variables and functions, the type can be specified by writing the name of the type followed by a : (colon).

myvar:float = 100

Assigning to a different type will result in a compile-time error, as shown below.

myvar:string = 100

In function type declarations, the return value can be specified by following the parameter parentheses with a -> between them.

fn add(x:float,y:float)->float{
  return x + y
In the case of this add function, we can predict that x and y are floats from the context [^binaryop], so we can omit it as follows.

fn add(x,y){
  return x+y

Primitive types

The only primitive types in mimium are float, string and void.

The only numeric type in mimium is float (internally a 64bit float). Integers can be used with the round, ceil, and floor functions.

Values of type string can be generated from double-quoted string literals, such as "hoge". Currently, it does not support string cutting or merging, and its usage is basically the same as

  1. pass it to the printstr function for debugging purposes. 2.

  2. pass it to the loadwav function to load an audio file. 3. pass it to include to include it.

  3. pass it to include to load other source files.

  4. pass to include to load other source files.

The void type has no value and is used to indicate that there is no return value for the function.

Composite types


An array is a type that can store multiple values of the same type in succession. It can be generated by comma-separated values enclosed in [] (angle brackets).

myarr = [1,2,3,4,5,6,7,8,9,10]

You can retrieve the value of an array type by specifying a zero-based index with angle brackets, such as myarr[0].

arr_content = myarr[0] //arr_content should be 1

You can also rewrite the contents of the array by using angle brackets on the left side value as well.

myarr[4] = 20 //myarr becomes [1,2,3,4,20,6,7,8,9,10].

**The size of the array is fixed. The size of the array is fixed, so you can’t add values to the back of the array. There is no bounds check, so out-of-range access will cause a crash. ** The size of the array is fixed.

Automatic interpolation

Indexes are automatically linearly interpolated when accessed with decimal values.

arr_content = myarr[1.5] //should be 2.5

There is no automatic rounding to integers, so if you want to avoid interpolation, you need to round the indices using the round function or something similar.


A tuple is a value that combines different types into one. They can be generated by enclosing variables in () (round brackets) and inserting comma-separated variables. Tuples are also similar to arrays, but each element can have a different type.

mytup = (100,200,300)

You can retrieve the value of a tuple by placing a comma-separated variable at the left-hand side value. There is no need to separate them with parentheses in this case.

one,two,three = mytup

Tuples are typically used in mimium to group together channels of audio signals such as stereo and multi-channel in signal processing.

Type Alias

Because type annotation for tuple can be redundant, it can be shorten using type alias semantics.

type FilterCoeffs = (float,float,float,float,float)

Struct(Record Type)

Struct has similar functionality to Tuple type but it can have field names for each type. Struct type cannot be anonymous type. Thus user needs to declare a type alias before initializing value and construct a variable with TypeName{val1,val2...}. The values can be extracted by dot operator like expr.field.

type MyBigStruct = {"field1":float,"field2":FilterCoeffs,"field3":string}

mystr = MyBigStruct{100,(0.0,1.0,1.2,0.8,0.4),"test"}



A function is a collection of reusable procedures that take multiple values and return a new value.

As an example, consider the add function, which just adds two values together and returns them.

To store it as a variable with an explicit type in mimium, write the following

fn add(x,y){
  return x+y

In mimium, functions can be treated as first-class values. This means that you can assign a function to a variable or take it as a parameter of a function.

For example, the type annotation of the previous add function is (float,float)->float. To assign the previous add function to a variable, you can write the following If you want to assign the function as a function parameter, see the section on higher-order functions.

my_function:(float,float)->float = add

Anonymous functions (lambda expressions)

The previous function declaration is actually an alias to the syntax for storing anonymous functions in variables, as shown below.

add = |x:float,y:float|->float{return x+y} 

It is also possible to call such a function directly without assigning it to a variable.

println(|x,y|{return x + y}(1,2)) //print "3"

Also, as will be explained in the block syntax section, the last line of the block can be substituted for return by simply placing an expression in place of return. In other words, the add function, combined with type inference, can be omitted until the following example.

add = |x,y|{x+y}

Pipe (|>) operators

In mimium, you can use the pipe operator |> to rewrite nested function calls like a(b(c(d))) as d |> c |> b |> a.

Looping by recursion

Named functions can also call themselves.

The fact function to compute the factorial can be defined as follows

fn fact(input:float){
    return 1
    return input * fact(input-1)

Use recursive functions with care, as they can cause infinite loops.


In a function, you can use a special keyword called self. self is a variable that can refer to the last value returned by a function. For example, the following function will return a value that increases by increment each time it is called.

fn counter(increment){
  return self+increment

Self is basically only available for functions that originate from the dsp function. self is initialized to 0 when the audio engine is started, and a separate value is created and managed for each calling context. For example, in the following example, the counter function is given a different increment for each of its functions, which internally allocates two pieces of memory for self, with lch increasing by 0.01 samples every time it crosses 1 and resetting to 0, and rch increasing by 0.05 samples every time it crosses 1.

fn dsp()->(float,float){
  lch = counter(0.01)%1
  rch = counter(0.05)%1
  return (lch,rch)

Scope of variables

mimium is a lexical-scoped language, which means that it is possible to refer to variables defined outside of a function.


Expressions, statements, and blocks

A collection of statements enclosed in curly braces {} used in a function, etc. is a unit called a block. A statement almost always consists of a syntax for assigning expressions, such as a = b. expression is a unit consisting of numbers like 1000, variable symbols like mynumber, arithmetic expressions like 1+2*3, and function calls with return values like add(x,y).

Block is actually one of the expressions. You can put multiple statements in a block, and the last line can use return to specify the value to be returned. The return keyword in the last line can also be omitted and just putting expression is allowed.

For example, the following syntax is grammatically correct. (*As of v0.3.0, this syntax is implemented incorrectly and does not work. *)

//mynumber should be 6
mynumber = {
  x = 2
  y = 4
  return x+y


Conditional in mimium has the syntax if (condition) then_expression else else_expression. condition, then_expression, and else_expression are all expressions. If the value of condition is greater than zero, the then_expression part is evaluated, otherwise the else_expression is evaluated.

If the then/else part is expressed as a block, it can be written in a C-like way as follows.

fn fact(input:float){
    return 1
    return input * fact(input-1)

On the other hand, the if statement itself can be treated as an expression, so the same syntax can be rewritten as follows. Note that the parentheses in the conditional part cannot be omitted.

fn fact(input:float){
  return if (input>0) 1 else input * fact(input-1)

Deferred execution with @ operator

You can defer the execution of a function by following the function call with @ followed by a value of numeric type. The unit of time is samples.

For example, the following example writes 100 and 200 to the standard output at the 0th and 48000th samples after starting the audio driver.


Currently, the @ operator can only be used for functions of type void (which have no return value).

By delaying the execution of a recursive function with @, it is also possible to repeat certain operations at regular intervals. For example, the following example will increment the number from 0 to 1 at 48000 sample intervals and write it to the standard output.

fn loopprint(input)->void{


The syntax include("path/to/file.mmm") allows you to include other files in the file.

The file path can be an absolute path or a path relative to the file. Currently, there is no namespace division, and the include statement is purely replaced by the text of the file (but once a file is loaded, it will not be loaded more than once).

Syntax definition by BNF, operator precedence, etc.


1.2.2 - Built-in Function

This section describes the built-in function in mimium.

This section describes the built-in function in mimium.


Returns delayed input value with the duration of time(unit: samples).

For example, the delay can be combined with self to create a feedback delay as shown below.

fn fbdelay(input:float,time:float,feedback:float){
    return delay(input*self*feedback,time)


Returns random value in a range of -1 to 1。An acutual implementation on C++ uses rand() function in C standard library like below.

 (double)rand() / RAND_MAX) * 2 - 1

Basic mathematical functions

Listed functions in math.h of C language is included in mimium by default.

Takes one float and returns one float if it has no explanation.

  • sin
  • cos
  • tan
  • asin
  • acos
  • atan
  • atan2 (x,y)
  • sinh
  • cosh
  • tanh
  • log
  • log10
  • exp
  • pow (x,y)
  • sqrt
  • abs
  • ceil
  • floor
  • trunc
  • round
  • fmod (x,y) % operator is an alias to this function.
  • remainder (x,y)
  • min (x,y) alias to fmin in C language.
  • max (x,y) alias to fmax in C language.

Mainly used for debugging purpose.

Print values to stdout. print,println accept number type as parameter. println output value with newline. You can output string type values by using printstr.

loadwav(path:string)->[float x 0] / loadwavsize(path:string)->float

Load audio files by using LibSndFile.

Both take the file path of the audio file (.wav, .aiff, .flac, etc.) as a parameter.

If the path is not absolute, it is interpreted as relative to the location of the source file.

loadwavsize(path) returns the number of samples of the audio file.

loadwav(path) returns the audio file as a read array. If you access the file with an index larger than the file size, it will crash, so you need to use the value of loadwavsize to limit the value.

2 - Developers Guide

Overall structure, C++ coding style and guideline for compiler&runtime development.


2.1 - Setup development environments

How to install dependency libraries, build source codes, debug and test.


  • cmake
  • bison 3.3~
  • flex
  • llvm 11~
  • libsndfile
  • rtaudio(cmake downloads automatically)

Optionally, Ninja is recommended for a fast build.


Install Xcode, and Xcode command line tools with the following command.

xcode-select --install

Install Homebrew by the instruction on the website.

Install dependencies with the following command.

brew tap mimium-org/mimium
brew install mimium -s --only-dependencies


If you are using Homebrew on Linux, you can use same installation command in the section of macOS.

If you want to install dependencies with apt, use the following command1.

pushd /tmp && wget && chmod +x && sudo ./ && popd
sudo apt-get install libalsa-ocaml-dev libfl-dev libbison-dev libz-dev libvorbis-dev libsndfile-dev libopus-dev gcc-9 ninja-build

Windows (on MSYS2)

Currently, build on Windows is realized by using MSYS2( Follow the instruction on MSYS2 website to install it.

Open MSYS MinGW64 terminal and install dependencies with the following command..

pacman -Syu --noconfirm git flex bison mingw-w64-x86_64-cmake mingw-w64-x86_64-gcc mingw64/mingw-w64-x86_64-libsndfile mingw64/mingw-w64-x86_64-opus mingw-w64-x86_64-ninja mingw-w64-x86_64-llvm

Clone the repository

Clone the repository of mimium with the git command.

git clone --recursive


For the development of mimium, using Visual Studio Code is recommended.

Open mimium.code-workspace with VSCode.

When you open the workspace, the pop-up menu will be shown to install recommended extensions if they are not installed.

  • cmake-tools
  • clangd
  • CodeLLDB
  • Coverage Gutter

Especially, CMake Tools is necessary to develop C++ project with VSCode.

Configure CMake Kit

When you open the workspace with the Cmake Tools installed, you will be asked which CMake kit you want to use (only at the first time).

If you are on macOS, choose /usr/bin/clang. Otherwise, choose an appropriate compiler you installsed, for example, /usr/local/bin/g++ on Linux, and /mingw64/bin/g++ on MSYS2.


Select the CMake Tools tab from the menu on the left side of VS Code, and select Configure All. A build directory will be created under build/ (RtAudio will be downloaded and built automatically at this time). Right next to Configure All, press Build All to start building all projects.

Build Targets

  • src/mimium_exe : Builds the main mimium command.
  • src/mimium : Builds the main body of the library, libmimium.
  • test/Tests : The target to build all tests (except Fuzzing).
  • Lcov LcovResetCounter : Target available when -DENABLE_COVERAGE is enabled. run the Lcov target after building and running one or more tests, etc. to collect coverage information. If you select Show Coverage from the Cmd+Shift+P command palette in this state, the actual execution of the code will be highlighted. After editing the source and rebuilding, you will need to run LcovResetCounter because of coverage information conflicts.

Debugging on VSCode

Select the Run tab from the menu on the left side of VS Code. Configurations can be selected from next to the Run button. There are two workspaces: one to launch the CMake target (“CMake Target Debug(Workspace)"), and another to run it with command line options (“Launch with Arg(edit this config)(workspace )").

You can choose which CMake target to launch by clicking “Select the target to launch” in the bottom menu bar.

If you want to launch by passing options to the command line, select “Launch with Arg(edit this config)(workspace)” and then use the gear symbol to directly edit the mimium.code-workspace file. For example, use “args” to specify the file name as shown in the following example.

		"name": "Launch with arg(edit this config)", 
		"type": "lldb",
		"request": "launch",
		"program": "${command:cmake.launchTargetPath}",
		"args": ["${workspaceFolder}/examples/gain.mmm"], 
		"cwd": "${workspaceFolder}/build", 

You can also pass the input from stdio by specifying like "stdio": ["${workspaceFolder}/stdin.txt",null,null],.


There are three main types of tests, using Google Test.

Unit tests

This is mainly a test to see if each section of the compiler works correctly by starting it alone.

Regression Test.

This is a test to invoke the actual built mimium binary from the std::system function and check if there are any errors in other sections due to the addition of new features. Since mimium does not currently have a syntax for verifying tests, we pipe the calculation results to standard output using the println function, and Google Test captures it to verify that the answer is correct. Also, the test which launches the audio driver is currently not implemented.

Fuzzing test

This is a fuzzing test that uses Clang’s libfuzzer. Fuzzing tests are used to verify that a random input (in this case, a string of source code) is given in a gradually changing manner, and that if the syntax is correct, it will be processed correctly, and if it is an error, it will be treated as an error and an unexpected crash will not occur.

It is only validated on macOS and is not included in CI.

Run Ctest

You can execute test command by running ctest command on build directory, or you can execute Unit Test and Regressin test from the menu on right-bottom of VSCode.

  1. On Linux(Ubuntu), we recommend installing llvm using an automatic installation script in because llvm package in apt does not contain Polly libs required by llvm-config --libs. ref ↩︎

2.2 - Coding Style

Coding styles used in a development of mimium

Basic Policy

  • language specification (LS) conforms to C++17.The main reason is why Code Template Inference improve readability such as if constexpr beacuse mimium use actively std::variant or std::optional.
  • **If you are uncertain about readability or a slight improvement in execution speed, take readability.**In the first place C++ is guranteerd to be reasonably fast, so it doesn’t matter if it can be a little rich processing, that degree of hesitation is about same when optimized.
  • Avoid using external libraries as much as possible(especialy for general purpose such as boost).And STL is actively used.
    • The compiler depends on bison(yacc) and flex(lex) as parser.This is especially valuable as bison source document,so we plan to continue using in the future, but there are problems Unicode not being able to be loaded for flex, I may move to REflex etc. or switch to manual implementation.Under consideration.
    • The runtime currently depends on libsndfile etc. for reading audio file, but we would like to separate it as a project structure later because it is only needed at runtime.
  • Mimium does not use raw pointers.Basically mimium uses std::shared_ptr<T>.But llvm::Type* in the LLVM library and llvm::Value* are not limited to this because they implement their own reference counting.
  • In the conditional expression(e.g.if block),mimium does not use the fact the pointer variable is empty with nullptr.Even if it takes some effort,the document value of the source code itself is improved by using std::optional<std::shared_ptr<T>>.

Dynamic Polymorphism

There are two types of polymorphism that switches indivisual processing for each type in C++: Static Polymorphism, which determines the type at compile time, and Dynamic Polymorphism, which determines the operation at runtime. Static Polymorphism is mainly implemented by templates, and Dynamic Polymorphism is mainly implemented by inheritance and virtual function.

However, the mimium development basically does not use virtual function for Dynamic Polymorphism.Instead, use std::variant introduced in STL since C++17.std::variant<T1,T2,T3...> is a type to which a variable having any of multiple types T1 to Tn can be substituted, and by using std::get<T> and std::visit(), it is possible to dynamically divide the processing according to the type.This is a substitute for the type called sum type that is often seen in functional types, and std::visit enables processing close to so-called pattern matching when combined processing division using templates and constexpr.In internal implementation, it is maximum memory of the type that can be taken and securing a tag (integer) of which type is currently held, so it is also called Tagged Union.




  • 継承した個別の型を基底クラスのポインターでダウンキャストして受け取る
  • 仮想関数を用いて型に応じた処理をする
  • 処理したあと帰ってきたポインターを元の型に戻し(アップキャスト)、さらに処理を続ける


またこうした(型に応じた処理を複数種類)x(複数の型)と組み合わせる方法はデザインパターンの中ではビジターパターンとも呼ばれ、 std::visit(function_object,variant_variable)ではこの形が引数としてシンプルに表されています。一方仮想関数を使ってのビジターパターンはデータ側にacceptと呼ばれるメソッドを実装しておく必要があるので、データはデータ、関数は関数というように構造を分離することが難しくなります。






Breaking Circular Dependencies in Recursive Union Types With C++17 - Don’t Compute In Public(last view:2020-08-17)

具体的には内部のTの実体を要素数1のstd::vector<T>に確保し、キャスト演算子としてT& ()を実装しimplicitに元の型から構築、キャストして参照を受け取ることができるようにしています。std::vectorTの中身が不完全なままでもスタック上のデータサイズを確定させることができるのでコンパイルが通るようになるのです。


using Value = std::variant<None, Void, Float, String, rRef, rTypeVar, rPointer, rFunction,rClosure, rArray, rStruct, rTuple, rAlias>;
using rFunction = Rec_Wrap<Function>;
struct Function : Aggregate {
  Value ret_type;
  std::vector<Value> arg_types;


types::Value operator()(types::Function& f){
    return  someProcess(f);
template<typename T>
types::Value operator()(Rec_Wrap<T>& t){
    return  (*this)(static_cast<T&>(t));

Rec_Wrap<T>を一度キャストして剥がしてもう一度自分自身を適用するテンプレート関数を使います。operator()(Rec_Wrap<types::Function>& rf)を直接オーバーロードしても構わないのですが、このrfは直接メンバアクセスができないため一度ローカル変数でtypes::Function&にキャストしてやらないといけなかったりする二度手間が発生します。





基本的にtry,catchはコンパイラでの処理のはじめに行い深くネストすることはしません。どの道、ほとんどのケースでエラーが起きれば最終的にコンパイルエラーの形に帰着するためです。必要に応じてエラークラスを継承して種類分けし、catchしたところでまとめてエラーの型ごとにメッセージ等を個別に処理します。( エラークラスの定義は今後の課題)

  1. std::variantの実装の元となったBoostには再帰データを扱えるrecursive_variantが存在していますが、今のところそのためだけにboostを利用するくらいならばヘルパークラスを一つ用意することで解決するという方針をとっています。 ↩︎

3 - Contributing

Contributing for mimium

Code of Conduct Contribution guide Documentation guide Community(gitter/twitter/etc)

3.1 - Code of Conduct

Purpose of the community and expected behavior as a participant


A primary goal of all communities such as a development group, other(e.g. documentation, financial) contributors, users group, related events, and so on) is to be inclusive to the largest number of contributors, with the most varied and diverse backgrounds possible.

As such, we are committed to providing a friendly, safe and welcoming environment for all, regardless of gender, sexual orientation, ability, nationality, language, age, ethnicity, socioeconomic status and religion (or lack thereof).

The mimium community strives to be:

  • Prioritize Diversity. We strive to be a community that welcomes and supports people of all backgrounds and identities.
  • Considerate: Your work will be used by other people, and you in turn will depend on the work of others. Any decision you take will affect users and colleagues, and you should take those consequences into account when making decisions.
  • Respect other communities. mimium has been made under the influence of many preceding languages, projects, and music/sound artworks. mimium is not made for surpassing or making them obsolete. We strive to grow our community and other various communities got involved with us to be more valuable through repetetive communication.

Expected Behavior as a member of the community

  • Participate in an authentic and active way. In doing so, you contribute to the health and longevity of this community.
  • Exercise consideration and respect in your speech and actions.
  • Attempt collaboration before conflict.
  • Be mindful of your surroundings and of your fellow participants. Alert community leaders if you notice a dangerous situation, someone in distress, or violations of this Code of Conduct, even if they seem inconsequential.
  • As the mimium community is a worldwide community, remember that people discussing with you may be using their non-primary language. Also, you need not hasitate speak your primary language if the language is not a major language used in the community.


  • You are invited to use our community to share your own projects and events, commercial or noncommercial, that directly involve mimium.
  • You may also share news of projects and events (for example, conferences, academic events, competitions) that are only topically related to mimium, provided that they are noncommercial.
  • Avoid using the community as a platform to advertise commercial products that lack direct connections to mimium.

Unacceptable Behavior

Unacceptable behaviors include: intimidating, harassing, abusive, discriminatory, derogatory or demeaning speech or actions by any participant in our community online, at all related events and in one-on-one communications carried out in the context of community business. Community event venues may be shared with members of the public; please be respectful to all patrons of these locations.

Harassment includes:

  • harmful or prejudicial verbal or written comments related to gender, sexual orientation, race, religion, disability
  • inappropriate use of nudity and/or sexual images (including presentation slides)
  • inappropriate depictions of violence (including presentation slides)
  • deliberate intimidation, stalking or following
  • harassing photography or recording
  • sustained disruption of talks or other events
  • inappropriate physical contact, and unwelcome sexual attention.

Consequences of Unacceptable Behavior

Unacceptable behavior from any community member, including sponsors and those with decision-making authority, will not be tolerated. Anyone asked to stop unacceptable behavior is expected to comply immediately.

If a community member engages in unacceptable behavior, the community organizers may take any action they deem appropriate, up to and including a temporary ban or permanent expulsion from the community without warning (and without refund in the case of a paid event).

If You Witness or Are Subject to Unacceptable Behavior

If you are subject to or witness unacceptable behavior, or have any other concerns, please notify a community organizer as soon as possible. You can find a list of organizers to contact for each of the supporters of this code of conduct at the bottom of this page. Additionally, community organizers are available to help community members engage with local law enforcement or to otherwise help those experiencing unacceptable behavior feel safe. In the context of in-person events, organizers will also provide escorts as desired by the person experiencing distress.

Addressing Grievances

If you feel you have been falsely or unfairly accused of violating this Code of Conduct, you should notify one of the community organizers with a concise description of your grievance. Your grievance will be handled in accordance with our existing governing policies.


We expect all community participants (contributors, paid or otherwise; sponsors; and other guests) to abide by this Code of Conduct in all community venues—online and in-person—as well as in all one-on-one communications pertaining to community business.

License and attribution

This Code of Conduct is distributed under a Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)」.

Also, This code of conduct is based on the following references.

Updating this Code of Conduct

Participants of the community should continue considering and discussing whether the code of conduct is appropriate for the current community. As necessary, update this code of conduct so that the community becomes better.


  • 2021/1/17 first version - mainly written by Tomoya Matsuura(@tomoyanonymous).

4 - Release Notes

Update/Deprecation infos on each update


New Language Feature

Struct type and type alias are introduced(#56).

type stereo = (float,float)
type composite = {signal:stereo , id:float}
fn test2(){
    ogya = composite{(100,200), 100}
    ho,fu = ogya.signal
    he =

Still, struct type has several limitations.

  • Embedding function type variable onto struct (and tuple) cannot be used for closure.
  • destructive assignment for struct variable by dot operator is not implemented yet(only a parser is implemented).


  • Fixed behavior of CLI when it could not find an input file path(#62,by @t-sin).


  • Some internal helper functions such as recursive variants are refined.



  • fixed a bug in code generator when if statement has void block(#51)
  • added missing == and != infix operators (#53)


  • ExecutionEngine class has been made by splitting from Runtime class toward implementing interpreter backend and environment variables feature.

New Function

Though this release is a patch release, a subtle new feature is added.

  • mem, a 1-sample delay function has been added. A simple example of biquad filter using this function is added to mimium-core/filter.mmm(#44).

Other updates

A list of all contributers is added to readme by using all-contributors.

v0.3.0 (2021-02-03)

New language features

Tuple and Array type

New aggregate type, tuple and array have been added.

Tuple type can be constructed with parenthesis and comma. Currently, the only way to get value of tuple type is like C++'s structural binding.

// Tuple Construction
triples = (100,200,300)//type signature is (float,float,float)

one,two,three = triples

In the future, dot access operator like triples.0 will be added.

Array type can be constructed with angle brackets and comma. Currently All the array is mutable , fixed sized and declared as a private global variable in llvm module. As a unique feature, an interpolation with floating pointer index is supported as same as reading audio files.

# Array Construction
myarr = [100,200,300]
internalv = myarr[0]//zero-based index
myarr[2] = 400//the array is now [100,200,400]
interp = myarr[0.5]//the result will be 150(linear interpolation)

Multichannel support for dsp function

Now mimium supports more than mono output, stereo and more many channels.

Numbers of inputs and outputs are determined by a type of dsp function. For example, stereo panning can be written like below.

fn panner(input:float,pan:float) -> (float,float){
    return (input*pan,input*(1-pan))

fn dsp(input:(float,float))->(float,float){
    src = random()*0.2
    res = panner(src,sin(5*now/48000)+1*0.5)
    return res

This is the breaking change because, 1. input parameter for dsp was time before v0.2 (this was a temporary solution before now was implemented), 2. output type for dsp was float but now the type for dsp should be (tuple of float)->(tuple of float), a function that takes 1 variable with tuple of floats and returns tuple of floats. Even if you want to process mono, the output type should be a tuple of 1 float.

Some examples were rewritten to match with this language spec.

Using mimium as C++ library

Dependencies of library headers and frontend(application instance and CLI) were tidied up. We can now use mimium as C++ Library. You can import mimium easily by using CMake. A minimal example is on

other changes

  • Supported version of LLVM is now 11.
  • was added.

v0.2.0 (2020-12-24)


  • Windows build(on MSYS2) is ready. Check GitHub Actions workflow if you want to build.
  • delay(input,delaytime) primitive function has been added.
    • maximum delay time is currently fixed to 44100 samples.
  • (experimental) a simple macro preprocessor has been added.
    • you can now include other source files with include "otherfile.mmm" put on a global context.
  • Refactored Mid-Level internal representation.

v0.1.5 (2020-09-28)

Fixed bugs

  • fixed a compile error when if statement contains only a single fcall inside braces(Thanks @t-sin).


  • Automatically copies changelog to release body in GitHub actions


Now new features such as delay primitive function which will be included in v0.2.0 are under development.

v0.1.4 (2020-09-11)

Fixed bugs

  • fixed compile error with a combination of clang & libstdc++.
  • fixed crashes on returning if as expression in function.


  • introduced address sanitizer and simple fuzzing test in develop environments.
  • memory allocations on user-code are freed on a destructor call of runtime.
    • heap allocations by user-code was not freed in previous versions but it’s not a serious problem because a program itself are exited when a destructor of runtime is called. This improvement makes sense mostly for a fuzzing test that iterates compilations many times in same process.

v0.1.3 (2020-09-09)

fixed bugs

  • fixed unusual crash when if-statement used on linux
  • fixed operator precedence of if statement when used as expression
// mathmatical operators have higher precedence than if or else!
myvar = if(cond) 100+20 else 200*50

v0.1.2 (2020-09-07)

fixed bugs

  • Previous release did not contain llvm generation for if statement. Now if statement/expression works correctly.
  • fixed a bug that comment-out which ends with a line break could not be parsed correctly.


MIR(Mid-Level Representation)-related classes’ implementation has been made more simplified. As like ast classes refined in v0.1.0, data does not have member functions and is initiallized with aggregate initialization.

v0.1.1 (2020-09-05)

Fixed Bug

This release mainly fixed a parser.

Now, a specification of block , statements inside curly-brackets is similar to Rust.

The block can be treated as just an expression, like function call or infix operations, when you put a single expression on last line of statements in block, or put return statement. That value becomes the block’s value itself.

Thus, all examples below is valid.

fn test(x,y){
    localvar = x*y+100
    localvar //last line is expression.
fn test(x,y){
    localvar = x*y+100
    return localvar //last line is return statement.

testvar = { velylocal = 100
            verylocal*2004} * 300 // this is also valid...

By this change, if statement can be both of an expression and a statement. When the contents of then/else statement do not have return value, it is just treated as like function of void type.

v0.1.0 (2020-08-21)

This release is mostly refactoring of internal processings, especialy AST(Abstract Syntax Tree)-related classes which was written in very early stage of development and is completely different style of implementation compared to newly introduced class such as MIR and Type related classes. A dynamic polymorphism in this compiler development is unified to the way using std::variant, not an class inheritance.

The release does neither contains new features nor breaking changes but fixed many instabilities, particularly incorrectness of type inference.

Also, build on Ubuntu has prepared. You can check dependencies from github action workflow page. Seeking people who can test on windows!

v0.0.0 (2020-02-15)

first release! no arrays, no structs, no include/modules. This is a “proof of concept” version of mimium.

known bugs

  • Calling same functions that uses self more than twice, instantiation of self will not be performed properly. (can avoid this behaviour by defining alias of function)
  • in dsp function, at least 1 global variable should be used.


  • if can have only a expression, not multiple statements(it’s like conditional operator((cond)? then_expr : else_expr) in other languages.)
  • array access [] can be used only for audio files loaded by using loadwav(path). No boundary checks for array access. You can get a size of the array by loadwavsize(path).