Using Lambdas in C++: Listing 1

Function variables in C.

// declarations of image saving functions in different formats.
int saveAsPNG(Image image, char* filepath) {
  ...
}

int saveAsGIF(Image image, char* filepath) {
  ...
}

int saveAsTIFF(Image image, char* filepath) {
  ...
}

int saveAsJPG(Image image, char* filepath) {
  ...
}

enum ImageType {Png, Gif, Tiff, Jpg};

// saveImageFunction_t is a pointer to a function that receives an image 
// and a filepath and returns int.
typedef int (*saveImageFunction_t)(Image image, char* filepath);

// saveFunctions is an array of the previous pointer to function type.
// Notice the order of initialization, similar to the enumation ImageType.
saveImageFunction_t saveFunctions[4] = {saveAsPNG, saveAsGIF, saveAsTIFF, saveAsJPG};

// the following line dereference the pointer and calls the JPG save function.
(*saveFunctions[Jpg])(im, "my_image");

About the Author

Diego Dagum is a software architect and developer with more than 20 years of experience. He can be reached at email@diegodagum.com.