text: /*
   * MIT License
   *
   *
   * Copyright (c) 2020 Temirkhan Myrzamadi
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   */
  
  #include <poica.h>
  
  #include <math.h>
  #include <stdio.h>
  
  // clang-format off
  interface(
      Shape,
      double (*area)(const void *self);
  );
  
  record(
      Square,
      field(width, double)
      field(height, double)
  );
  
  record(
      Triangle,
      field(a, double)
      field(b, double)
      field(c, double)
  );
  
  impl(
      (Shape) for (Square),
      (double)(area)(const void *self)(
          const Square *square = (const Square *)self;
          return square->width * square->height;
      )
  );
  
  impl(
      (Shape) for (Triangle),
      (double)(area)(const void *self)(
          const Triangle *triangle = (const Triangle *)self;
          double a = triangle->a, b = triangle->b, c = triangle->c;
  
          double p = (a + b + c) / 2;
          return sqrt(p * (p - a) * (p - b) * (p - c));
      )
  );
  // clang-format off
  
  /*
   * Output:
   * 20.400000
   * 24.000000
   */
  int main(void) {
      const Square square = { .width = 6, .height = 3.4 };
      const Triangle triangle = { .a = 4, .b = 13, .c = 15};
  
      printf("%f\n", iMethods(Shape, Square).area(&square));
      printf("%f\n", iMethods(Shape, Triangle).area(&triangle));
  }
  