🧮 PyCer

PyCer, a Python to C++ compiler written in Python. Heavily based on Polyakov Konstantin's py2c project.

ℹ About

PyCer is a Python transpiler which syntatically transpiles Python code to Pure C++ code. Note that it does not semantically transpile. Instead it compiles the Python's syntatic constructs to C++'s equivalent. This project is not intended to be a pure Python compiler like Cython or Nutika(with lots of optimisations). But to be a lightweight transpiler. This projects intends to give a good API and a frontend for the base Transpiler.

Things to note

As previously stated, this project syntatically transpiles Python code to C++ code.

For example:

# python
i: int = int(input("Hola"))

would be translated to:

// c++
int i = int(input("Hola"));

Think this project as a extension to existing C++ where the user can write C++ code using Python's syntax.

Restrictions:

• Types must always be declared through annotation during initialization.
• Type annotation will work if it is specified before the assignment. If it is specified at or after the assignment, the annotation will be ignored.
• All arguments are mandatory (there are plans to add the ability to specify default arguments).
• By default, all positive integers have the C-type int.
• Strings have the default type of std::string.
• Arrays of pointers are currently impossible
• The string PTR will get replaced with * after translation, so may not be used in variable names

Required additions to Python syntax

Obviously, C++ has some different features to Python, and so some extra features have had to have been added to extend the syntax:

Pointers and references

To declare a pointer, add the text PTR to the end of the type, and to use a reference, use the REF(value) macro:

# python
myStr: str = "Hello, world!"
myPtr: strPTR = REF(str)
print(myPtr)

Gets translated to:

// c++
std::string myStr = "Hello, world!";
std::string *myPtr = &myStr;
print(myPtr); // this goes to a function defined in the preamble

Array types

To define an array you can just use the standard non-array type with a python list, however when you need to access the array type for functions, you should add the string _ARRx to the end of the type, where x is the amount of elements. x can be omitted if wanted.

# python
def example(arr: strPTR) -> strPTR:
    result: strPTR = ptr(string, malloc(2 * sizeof(string))) # macro: ((type *) (value))

    if result == NULL: # memory safety is important!
        print("Memory allocation failed!")
        return NULL

    result[0] = arr[1]
    result[1] = arr[0]

    return result

def main() -> int:
    arr1: str = ["hello, world", "element 2.1"]
    arr2: str_ARR2 = ["hello, world again", "element 2.2"]
    arr3: str_ARR = ["hello, world again again", "element 2.3"]

    retArr: strPTR = example(arr1)
    for i in range(2):
        print("Element",str(i)+":",retArr[i])

Translated to:

// C++
string* example(string* arr) {
    string* result = ptr(string, malloc(2 * sizeof(string)));
    if (result == NULL) {
        print("Memory allocation failed!");
        return NULL;
    }
    result[0] = arr[1];
    result[1] = arr[0];
    return result;
}
int main(void) {
    string arr1[] = {"hello, world", "element 2.1"};
    string arr2[2] = {"hello, world again", "element 2.2"};
    string arr3[] = {"hello, world again again", "element 2.3"};
    string* retArr = example(arr1);
    for (int i=0; i<2; i++) {
        print("Element", str(i) + ":", retArr[i]);
    }
}

📃 Requirements

• Python >= 3.6
• Any C++ compiler, to compile the produced C++ code to native binary
  • When executed with Pycer, g++ is used, and is recommended, but any C++ compiler will do

✍🏻 Authors and acknowledgment

I would like to thank Polyakov Konstantin for his work on py2c project.

This project is currently edited and maintained by Harish Kumar. Some features such as pointers, references and arrays have been implemented by develop331.

⏳ Project Status

This project is currently in development.

📝 License

This project is GPLv3 licensed.