mys 0.74.0

The Mys (/maɪs/) programming language.

🐁 Mys

The Mys (/maɪs/) programming language - an attempt to create a statically typed Python-like language that produces fast binaries.

Mys is heavily inspired by Python’s syntax and Rust’s packaging.

from random.pseudo import random

def main():
    print(random())

[package]
name = "robot"
version = "0.1.0"

[dependencies]
random = "*"

Mys is mainly targeting resource constrained single and multi core embedded systems.

Project homepage: https://github.com/eerimoq/mys

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IMPORTANT INFORMATION

The language and build system implementation is still in a very early stage. Some arithmetic, print and conditional statements works, but not much more.

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Quick start

Installation

Install Python 3.6 or later, and then install Mys using pip.

$ pip install mys

You must also have recent versions of g++, make and pylint installed.

Tutorial

First of all, create a package called foo with the command mys new foo, and then enter it. This package is used in throughout the tutorial.

src/main.mys implements the hello world application. This file is only part of application packages (executables).

def main():
    print("Hello, world!")

Build and run the application with the command mys run. It prints Hello, world!, just as expected.

src/lib.mys implements the function add() and it’s test test_add(). This file is normally part of both application and library packages.

def add(first: i32, second: i32) -> i32:
    return first + second

@test
def test_add():
    assert_eq(add(1, 2), 3)

Build and run the tests with the command mys test.

Add the bar package as a dependency and use it’s hello() function.

package.toml with the bar dependency added:

[package]
name = "foo"
version = "0.1.0"
authors = ["Mys Lang <[e-mail]>"]

[dependencies]
bar = "*"

src/main.mys importing hello() from the bar module:

from bar import hello

def main(argv: [string]):
    hello(argv[1])

Build and run the new application. Notice how the dependency is downloaded and that mys run universe prints Hello, universe!.

Replace the code in src/main.mys with the code below. It examplifies how to use functions, classes, exceptions, types and command line arguments. The syntax is almost identical to Python, so most readers should easily understand it.

NOTE: This code does not yet work. This is just an example of what an application could look like in the future. The Fibonacci example works, so try that instead!

def func_1(a: i32) -> (i32, string):
    return 2 * a, "Bar"

def func_2(a: i32, b: i32 = 1) -> i32:
    for i in range(b):
        a += i * b

    return a

def func_3(a: i32) -> {i32: [f32]}:
    return {
        1: [],
        10 * a: [7.5, -1.0]
    }

def func_4():
    try:
        raise Error()
    except:
        print("func_4():      An error occurred.")

def func_5() -> [i32]:
    small: [i32] = []

    for v in [3, 1, 5, 7, 2]:
        if v < 5:
            small.append(v)

    small.sort()
    small.reverse()

    return small

class Calc:

    value: i32

    def triple(self):
        self.value *= 3

def main(argv: [string]):
    value = i32(argv[1])
    print("func_1(value):", func_1(value))
    print("func_2(value):", func_2(value))
    print("func_3(value):", func_3(value))
    func_4()
    print("func_5():     ", func_5())
    calc = Calc(value)
    calc.triple()
    print("calc:         ", calc)

Build and run it.

$ mys run 5
func_1(value): (5, "Bar")
func_2(value): 7
func_3(value): {1: [], 50: [7.5, -1,0]}
func_4():      An error occurred.
func_5():      [3, 2, 1]
calc:          Calc(value=15)

Types

Primitive types

Primitive types are always passed by value.

Type	Example	Comment
i8, i16, i32, i64	1, -1000	Signed integers of 8, 16, 32 and 64 bits.
u8, u16, u32, u64	1, 1000	Unsigned integers of 8, 16, 32 and 64 bits.
f32, f64	5.5, -100.0	Floating point numbers of 32 and 64 bits.
bool	True, False	A boolean.
char	'a'	A unicode character. '' is not a character.

i8, i16, i32, i64, u8, u16, u32 and u64

iN(number: string)             # String to signed integer.
uN(number: string)             # String to unsigned integer.
iN(value: f32/f64)             # Floating point number to signed integer.
uN(value: f32/f64)             # Floating point number to unsigned integer.
iN(value: bool)                # Boolean to signed integer (0 or 1).
uN(value: bool)                # Boolean to unsigned integer (0 or 1).
i32(value: char)               # Character to singed integer.
==                             # Comparisons.
!=
<
<=
>
>=
^                              # Bitwise exclusive or.
&                              # Bitwise and.
|                              # Bitwise or.
+                              # Add.
-                              # Subtract.
*                              # Multiply.
/                              # Divide (round down).
%                              # Modulus.
~                              # Complement.
^=                             # Bitwise exclusive or in place.
&=                             # Bitwise and in place.
|=                             # Bitwise or in place.
+=                             # Add in place.
-=                             # Subtract in place.
*=                             # Multiply in place.
/=                             # Divide in place.
%=                             # Modulus in place.
~=                             # Complement in place.

f32 and f64

fN(number: string)      # String to floating point number.
fN(value: iN/uN)        # Integer to floating point number.
fN(value: bool)         # Boolean to floating point number (0 or 1).
==                      # Comparisons.
!=
<
<=
>
>=
+                       # Add.
-                       # Subtract.
*                       # Multiply.
/                       # Divide.
+=                      # Add in place.
-=                      # Subtract in place.
*=                      # Multiply in place.
/=                      # Divide in place.

bool

bool(value: iN/uN)    # Integer to boolean. 0 is false, rest true.
bool(value: f32/f64)  # Floating point number to boolean. 0.0 is false,
                      # rest true.

char

char(number: i32)
+=(value: i32)                    # Add given value.
+(value: i32) -> char             # Add given value.
-=(value: i32)                    # Subtract given value.
-(value: i32) -> char             # Subtract given value.
==                                # Comparisons.
!=
<
<=
>
>=

Complex types

Complex types are always passed by reference.

Type	Example	Comment
string	"Hi!"	A sequence of unicode characters.
bytes	b"\x00\x43"	A sequence of bytes.
tuple(T1, T2, ...)	(5.0, 5, "foo")	A tuple with items of types T1, T2, etc.
list(T)	[5, 10, 1]	A list with items of type T.
dict(TK, TV)	{5: "a", -1: "b"}	A dictionary with keys of type TK and values of type TV.
class Name	Name()	A class.

string

__init__()                              # Create an empty string. Same as "".
__init__(character: char)               # From a character.
__init__(other: string)                 # From a string.
__init__(length: u64)
length(self) -> u64                     # Its length.
to_utf8(self) -> bytes                  # To UTF-8 bytes.
from_utf8(utf8: bytes) -> string
to_lower(self) -> string                # Return a new lower case string.
to_upper(self) -> string                # Return a new upper case string.
+=(self, value: string)                 # Append a string.
+=(self, value: char)                   # Append a character.
+(self, value: string) -> string        # Add a string.
+(self, value: char) -> string          # Add a character.
==(self)                                # Comparisons.
!=(self)
<(self)
<=(self)
>(self)
>=(self)
*(self, count: u64)                     # Repeat.
*=(self, count: u64)                    # Repeat in place.
[]=(self, index: u64, character: char)  # Set a character.
[](self, index: u64) -> char            # Get a character.
[]=(self,                               # Set a substring.
    begin: u64,
    end: u64,
    step: u64,
    value: string)
[](self,                                # Get a substring.
   begin: u64,
   end: u64,
   step: u64) -> string
__in__(self, value: char) -> bool       # Contains character.
__in__(self, value: string) -> bool     # Contains string.
starts_with(self,
            substring: string) -> bool
split(self,
      separator: string) -> [string]
join(parts: [string],                   # From list of strings and separator. Inverse
     separator: string = "")            # of split().
strip(self, chars: string)              # Strip leading and trailing characters in place.
lower(self, self)                       # Make it lower case.
upper(self, self)                       # Make it upper case.
find(self,                              # Find the first occurrence of given separator
     separator: char,                   # within given limits. Returns -1 if not found.
     start: i64 = 0,
     end: i64 = -1) -> i64
cut(self,                               # Find the first occurrence of given separator.
    separator: char) -> string          # If found, returns all characters before that,
                                        # and remove them and the separator from the
                                        # string. Returns None and leaves the string
                                        # unmodified otherwise.
replace(self,                           # Replace old with new.
        old: char,
        new: char)
replace(self,                           # Replace old with new.
        old: string,
        new: string)

Only += moves existing data to the beginning of the buffer. Other methods only changes the begin and/or end position(s). That is, strip() and cut() are cheap, but += may have to move the data.

bytes

__init__()                         # Create an empty bytes object. Same as b"".
__init__(other: bytes)             # From a bytes object.
__init__(length: u64)
length(self) -> u64                # Its length.
to_hex(self) -> string             # To a hexadecimal string.
from_hex(data: string) -> bytes
+=(self, value: bytes)             # Append bytes.
+=(self, value: u8)                # Append a number (0 to 255).
+(self, value: bytes) -> bytes     # Add bytes.
+(self, value: u8) -> bytes        # Add a number (0 to 255).
==(self)                           # Comparisons.
!=(self)
<(self)
<=(self)
>(self)
>=(self)
[]=(self, index: u64, value: u8)
[](self, index: u64) -> u8
[]=(self,
    begin: u64,                    # Set subbytes.
    end: u64,
    step: u64,
    value: bytes)
[](self,
   begin: u64,                     # Get subbytes.
   end: u64,
   step: u64) -> bytes
__in__(self, value: u8) -> bool    # Contains value.

tuple

==(self)                         # Comparisons.
!=(self)
<(self)
<=(self)
>(self)
>=(self)
[]=(self, index: u64, item: TN)  # Set item at index. The index  must be known at
                                 # compile time.
[](self, index: u64) -> TN       # Get item at index. The index must be known at
                                 # compile time.

list

__init__()                      # Create an empty list. Same as [].
__init__(other: [T])            # From a list.
__init__(length: u64)
length(self) -> u64             # Its length.
+=(self, value: [T])            # Append a list.
+=(self, value: T)              # Append an item.
==(self)                        # Comparisons.
!=(self)
<(self)
<=(self)
>(self)
>=(self)
[]=(self, index: u64, item: T)
[](self, index: u64) -> T
[]=(self,                       # Set a sublist.
    begin: u64,
    end: u64,
    step: u64,
    value: [T])
[](self,                        # Get a sublist.
   begin: u64,
   end: u64,
   step: u64) -> [T]
__in__(self, item: T) -> bool   # Contains item.
sort(self)                      # Sort items in place.
reverse(self)                   # Reverse items in place.

dict

__init__()                     # Create an empty dictionary. Same as {}.
__init__(other: {TK: TV})      # From a dict.
__init__(pairs: [(TK, TV)])    # Create from a list.
==(self)                       # Comparisons.
!=(self)
[]=(self, key: TK, value: TV)  # Set value for key.
[](self, key: TK) -> TV        # Get value for key.
|=(self, other: {TK: TV})      # Set/Update given key-value pairs.
|(self, other: {TK: TV})       # Create a dict of self and other.
__in__(self, key: TK) -> bool  # Contains given key.

Built-in functions

Name	Example	Comment
input()	input("> ")	Print prompt and read input until newline.
open()	open("path/to/file")	Opens given file in given mode.
print()	print("Hi!")	Prints given data.
range()	range(10)	A range of numbers.
str()	str(10)	Printable represenation of given object.

Packages

A package contains modules that other packages can use. All packages contains a file called lib.mys, which is imported from with from <package> import <function/class/variable>.

There are two kinds of packages; library packages and application packages. The only difference is that application packages contains a file called src/main.mys, which contains the application entry point def main(...). Application packages produces an executable when built (mys build), libraries does not.

A package:

my-package/
├── LICENSE
├── package.toml
├── pylintrc
├── README.rst
└── src/
    ├── lib.mys
    └── main.mys         # Only part of application packages.

The mys command line interface:

mys new      Create a new package.
mys build    Build the appliaction.
mys run      Build and run the application.
mys test     Build and run tests.
mys clean    Remove build output.
mys lint     Perform static code analysis.
mys publish  Publish a release.

Importing functions and classes

Import functions, classes and variables from other packages with from <package>[[.<sub-package>]*.<module>] import <function/class/variable>.

Import functions, classes and variables from current package with from .+[[<sub-package>.]*<module>] import <function/class/variable>. One . per directory level.

Use from ... import ... as <name> to use a custom name.

Here are a few examples:

from mypkg1 import func1
from mypkg2.subpkg1.mod1 import func2 as func3
from mypkg2 import Class1
from mypkg2 import var1
from .mod1 import func4           # ../mod1.mys
from ...mypkg3.mod1 import func5  # ../../../mypkg3/mod1.mys

def foo():
    func1()
    func3()
    Class1()
    print(var1)
    func4()
    func5()

List of packages

• argparse - Command line argument parser.

• bits - Basic bits operations.

• log - Logging facilities.

• math - Basic math operations.

• random - Random numbers.

• system - System services.

• time - Date and time.

Extending Mys with C++

Extending Mys with C++ is extremly easy and flexible. Strings that starts with mys-embedded-c++ are inserted at the same location in the generated code.

def main():
    a: i32 = 0

    """mys-embedded-c++

    i32 b = 2;
    a++;
    """

    print("a + b:", a + b)

Loops

while and for loops are available.

while loops run until given condition is false or until break.

for loops can only iterate over ranges, lists, dictionaries, strings and bytes. Each item index is optionally available.

# While.
v = 0

while v < 10:
    if v < 3:
        continue
    elif v == 7:
        break

    v += 1

# Ranges.
for v in range(10):
    if v < 3:
        continue
    elif v == 7:
        break

for i, v in range(4, 10, -2):
    pass

# Lists.
for v in [3, 1]:
    pass

for i, v in [3, 1]:
    pass

# Dictionaries.
for k, v in {2: 5, 6: 2}:
    pass

for i, (k, v) in {2: 5, 6: 2}:
    pass

# Strings.
for c in "foo":
    pass

for i, c in "foo":
    pass

# Bytes.
for b in b"\x03\x78":
    pass

for i, b in b"\x03\x78":
    pass

Dynamic dispatch

Call function or method with matching parameter(s). Always calls the most specialized function or method.

Interface for generics.

class Message:
    pass

class Foo(Message):
    pass

class Bar(Message):
    pass

class Fie(Message):
    pass

def handle(message: Foo):
    print("Handling foo.")

def handle(message: Bar):
    print("Handling bar.")

def handle(message: Message):
    print("Unhandled message: {message}")

def handle_message(message: Message):
    # Calls one of the three handle functions above based on the
    # message type. Always calls the most specialized function.
    handle(message)

def main():
    handle_message(Foo())
    handle_message(Bar())
    handle_message(Fie())

$ mys run
Handling foo.
Handling bar.
Unhandled message: Fie()

Memory management

Integers and floating point numbers are allocated on the stack, passed by value to functions and returned by value from functions, just as any C++ program.

Strings, bytes, tuples, lists, dicts and classes are normally allocated on the heap and managed by C++ shared pointers. Objects that are known not to outlive a function are allocated on the stack.

Reference cycles are not detected and will result in memory leaks.

There is no garbage collector.

Classes

• Instance members are accessed with self.<variable/method>.

• Overridden methods must be decorated with @override.

• Use @override(T) to override the method from class T. Useful if two parent classes have methods with the same name.

• Automatically added methods (__init__(), __str__(), …) are only added if missing.

Below is a class with a data member value and a method inc().

The constructor def __init__(self, value: i32 = 0) (and more methods) are automatically added to the class as they are missing.

class Foo:

    value: i32

    def inc(self):
        self.value += 1

def main():
    print("f1:")
    f1 = Foo()
    print(f1)
    f1.inc()
    print(f1)

    print("f2:")
    f2 = Foo(5)
    print(f2)

$ mys run
f1:
Foo(value=0)
Foo(value=1)
f2:
Foo(value=5)

Build options

--optimize {speed, size, debug}: Optimize the build for given level. Optimizes for speed by default.

--unsafe: Disable runtime safety checks for faster and smaller binaries.

Disables:

• Implicit None checks.

• list, string and bytes out of bounds checks.

• Signed integer overflow checks.

• Default variable and data member initializations.

• Message ownership checks.

Text editor settings

Visual Code

Use the Python language for *.mys files by modifying your files.associations setting.

See the official Visual Code guide for more detils.

"files.associations": {
    "*.mys": "python"
}

Emacs

Use the Python mode for *.mys files by adding the following to your .emacs configuration file.

(add-to-list 'auto-mode-alist '("\\.mys\\'" . python-mode))

Build process

mys build, mys run and mys test does the following:

1. Use Python’s parser to transform the source code to an Abstract Syntax Tree (AST).

2. Generate C++ code from the AST.

   Probably generate three files:

   • <module>.mys.types.hpp, which contains forward declarations of all types.

   • <module>.mys.hpp, which contains all declarations.

   • <module>.mys.cpp, which contains the implementation.

   Goals:

   • Only make methods virtual if overridden by another class.

   • Remove all unused functions, methods and variables. Should remove test helper functions.

3. Compile the C++ code with g++.

4. Link the application with g++.