#include char input[50]; int main() { do { } while (loop_for_input(&input) != 0); return 0; } int loop_for_input(char **input) { printf("Enter reverse polish notation string to process. End with return. Type 'n' or 'N' to quit\n"); return 0; } // rpncalc.c: In function 'int main()': // rpncalc.c:24: error: 'loop_for_input' was not declared in this scope