Monads/List monad: Difference between revisions

=={{header|C}}==

The C type which best fits the concept used here for <code>monad</code> would be <code>void*</code>.

There's some limitations -- the list type characteristics in this context, if they had been used, would have required special attention to issues like traversing the list. And, C does not provide syntactic sugar which a user would likely expect from experience in some other languages.

Still, the task example is constrained enough that we can provide an implementation like:

<lang C>#include <stdio.h>

#include <stdlib.h>

#define MONAD void*

#define INTBIND(f, g, x) (f((int*)g(x)))

#define RETURN(type,x) &((type)*)(x)

MONAD boundInt(int *x) {

return (MONAD)(x);

}

MONAD boundInt2str(int *x) {

char buf[100];

char*str= malloc(1+sprintf(buf, "%d", *x));

sprintf(str, "%d", *x);

return (MONAD)(str);

}

void task(int y) {

char *z= INTBIND(boundInt2str, boundInt, &y);

printf("%s\n", z);

free(z);

}

int main() {

task(13);

}</lang>

Which, from the command line, might look like:

<lang bash>$ ./monad

13</lang>