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/* enum1.c -- Starting to use enumerated types: Printing for each
* day of the week, today, yesterday, and tomorrow, both
* as a string and as a number.
*/
#include <stdio.h>
/* Introducing an enumerated data type */
enum days {monday,tuesday,wednesday,thursday,friday,saturday,sunday};
typedef enum days days; // This allows us to use "days" as an abbreviation
// for "enum days"
/* Two useful functions */
days yesterday(days today){
return (today+6)%7;
}
days tomorrow(days today){
return (today+1)%7;
}
// A useful array: thedays is an array of constant (i.e you cannot
// modify them) pointers to constant (i.e. you cannot modify them) strings
const char * const thedays[] =
{"monday", "tuesday", "wednesday", "thursday",
"friday", "saturday", "sunday"};
int main(void){
days today;
printf("today \tyesterday \ttomorrow\n"
"============================================\n");
for (today=monday;today<=sunday;today++)
printf("%s = %d \t %s = %d \t %s = %d\n",
thedays[today], today,
thedays[yesterday(today)], yesterday(today),
thedays[tomorrow(today)], tomorrow(today));
}
/*
The output is:
today yesterday tomorrow
============================================
monday = 0 sunday = 6 tuesday = 1
tuesday = 1 monday = 0 wednesday = 2
wednesday = 2 tuesday = 1 thursday = 3
thursday = 3 wednesday = 2 friday = 4
friday = 4 thursday = 3 saturday = 5
saturday = 5 friday = 4 sunday = 6
sunday = 6 saturday = 5 monday = 0
*/
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