From ce588670229cc68cebe4d93b19e9bc2c6f3c65cd Mon Sep 17 00:00:00 2001 From: zlg Date: Sun, 15 Sep 2013 10:17:40 -0500 Subject: Solve Exercise 5-8: Checking for errors --- ch5/5-08_error-checking.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) create mode 100644 ch5/5-08_error-checking.c (limited to 'ch5/5-08_error-checking.c') diff --git a/ch5/5-08_error-checking.c b/ch5/5-08_error-checking.c new file mode 100644 index 0000000..61c15c7 --- /dev/null +++ b/ch5/5-08_error-checking.c @@ -0,0 +1,83 @@ +#include + +/* The C Programming Language: 2nd Edition + * + * Exercise 5-8: There is no error checking in day_of_year or month_day. + * Remedy this defect. + * + */ + +static char daytab[2][13] = { + {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}, + {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31} +}; + +int day_of_year(int year, int month, int day); +void month_day(int year, int yearday, int *pmonth, int *pday); + +int main() { + int m, d, doy; + m = d = 0; + doy = 0; + + printf("Calling day_of_year(1973, 10, 32)\n> "); + if ((doy = day_of_year(1973, 10, 32)) > 0) { + printf("Oct 12nd, 1973 is day %d\n", doy); + } else { + printf("The month or day is out of range!\n"); + } + printf("Calling month_day(1985, 295, ...)\n> "); + month_day(1985, 295, &m, &d); + if (m > 0 && d > 0) { + printf("Day 295 of year 1985 is month %d and day %d\n", m, d); + } else { + printf("month_day: day of year out of range!\n"); + } + printf("Calling day_of_year(1492, 5, 14)\n> "); + if ((doy = day_of_year(1492, 5, 14)) > 0) { + printf("May 14th, 1492 is day %d\n", doy); + } else { + printf("The month or day is out of range!\n"); + } + printf("Calling month_day(2012, 367, ...)\n> "); + month_day(2012, 367, &m, &d); + if (m > 0 && d > 0) { + printf("Day 295 of year 1985 is month %d and day %d\n", m, d); + } else { + printf("month_day: day of year out of range!\n"); + } + return 0; +} + +int day_of_year(int year, int month, int day) { + int i, leap; + leap = (year % 4 == 0 && year % 100 != 0) || year % 400 == 0; + + if (month < 1 || month > 12) { + return -1; + } + if (day > daytab[leap][month] || day < 1) { + return -1; + } + for (i = 1; i < month; i++) { + day += daytab[leap][i]; + } + return day; +} + +void month_day(int year, int yearday, int *pmonth, int *pday) { + int i, leap; + leap = (year % 4 == 0 && year % 100 != 0) || year % 400 == 0; + + // Check for edge case + if (yearday > 365 + leap || yearday < 1) { + *pmonth = 0; // Set to zero so the error is obvious + *pday = 0; + return; + } + for (i = 1; yearday > daytab[leap][i]; i++) { + yearday -= daytab[leap][i]; + } + *pmonth = i; + *pday = yearday; +} -- cgit v1.2.3-54-g00ecf