Add C support for a class containing only scalar data

[EmilyBourne]

Relevant Discussion

#1119

Describe the feature

Add support for classes as simple objects containing scalars. It may be a good idea to implement this issue after #1441 as functions will be useful for the constructor.

Test Code

Provide code which does not currently work but which should do when this issue is fixed:

# pylint: disable=missing-class-docstring,  missing-function-docstring, missing-module-docstring
#$ header class Point(public)
#$ header method __init__(Point, double, double)

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

if __name__ == '__main__':
    p = Point(0.0, 0.0)
    x=p.x
    p.x=4
    a = p.x
    a = p.x - 2
    a = 2 * p.x - 2
    a = 2 * (p.x + 6) - 2

    p.y = a + 5
    p.y = p.x + 5

    print(p.x, p.y)
    print(x)
    print(a)

Proposed Solution

The printing stage should generate the following header code:

#ifndef TEST_MOD_H
#define TEST_MOD_H

#include <stdlib.h>
#include "ndarrays.h"

struct Point {
    double x;
    double y;
};

void Point__init(struct Point self, double x, double y);
#endif // TEST_MOD_H

and the appropriate associated source code.

Target Language

C

Acceptance Criteria

To complete this issue the following should be done:

• Add test(s) similar to the one above in tests/pyccel/scripts/classes
  • Ensure that the tests are run and work for Fortran in tests/pyccel/test_pyccel.py
  • Ensure that the test can also be run for C (should not pass yet)
• Implement _print_ClassDef to handle the subset of classes described above