Solve Exercise 2-01: Variable limits

Fixed gitignore list, too

1 files changed, 142 insertions, 0 deletions

diff --git a/ch2/2-01_limits.c b/ch2/2-01_limits.c
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+#include <stdio.h>
+#include <limits.h>
+#include <float.h>
+
+/* The C Programming Language, 2nd Edition
+ *
+ * Exercise 2-1: Write a program to determine the ranges of char, short,
+ * int, and long variables, both signed and unsigned, by printing
+ * appropriate values from standard headers and by direct computation.
+ * Harder if you compute them: determine the ranges of the various
+ * floating-point types.
+ *
+ * Answer: The trick to computing these numbers is to understand computer math,
+ * which is done in binary, thus with 2. Keep squaring from 1 and you'll
+ * eventually find the limit of the variable. Add or subtract from one of the
+ * extremes and you'll find the other extreme.
+ *
+ */
+
+int main() {
+	unsigned char uc;
+	signed char sc;
+	unsigned short us;
+	signed short ss;
+	unsigned int ui;
+	signed int si;
+	unsigned long ul;
+	signed long sl;
+	unsigned long long ull;
+	signed long long sll;
+	float fl, fla, fll;
+	double db, dba, dbl;
+	long double ldb, ldba, ldbl;
+
+	printf("Let's compute the minimums and maximums of each type!\n");
+	uc = sc = us = ss = ui = si = ul = sl = sll = ull = 0;
+	fl = fla = fll = db = dba = dbl = ldb = ldba = ldbl = 0.0;
+
+	/* Characters */
+
+	sc++;
+	while (sc * 2 > sc) {
+		sc = sc * 2 + 1;
+	}
+
+	printf("`signed char` maximum: %d\n", sc);
+	sc++;
+	printf("`signed char` minimum: %d\n", sc);
+	uc--;
+	printf("`unsigned char` maximum: %u\n", uc);
+
+	/* Short ints */
+
+	ss++;
+	while (ss * 2 > ss) {
+		ss = ss * 2 + 1;
+	}
+
+	printf("`signed short` maximum: %d\n", ss);
+	ss++;
+	printf("`signed short` minimum: %d\n", ss);
+	us--;
+	printf("`unsigned short` maximum: %u\n", us);
+
+	/* Integers */
+
+	si++;
+	while (si * 2 > si) {
+		si = si * 2 + 1;
+	}
+
+	printf("`signed int` maximum: %d\n", si);
+	si++;
+	printf("`signed int` minimum: %d\n", si);
+	ui--;
+	printf("`unsigned int` maximum: %u\n", ui);
+
+	/* Long ints */
+
+	sl++;
+	while (sl * 2 > sl) {
+		sl = sl * 2 + 1;
+	}
+
+	printf("`signed long` maximum: %li\n", sl);
+	sl++;
+	printf("`signed long` minimum: %li\n", sl);
+	ul--;
+	printf("`unsigned long` maximum: %lu\n", ul);
+
+	/* Long long ints */
+
+	sll++;
+	while (sll * 2 > sll) {
+		sll = sll * 2 + 1;
+	}
+
+	printf("`signed long long` maximum: %lli\n", sll);
+	sll++;
+	printf("`signed long long` minimum: %lli\n", sll);
+	ull--;
+	printf("`unsigned long long` maximum: %llu\n", ull);
+
+	/* Floats */
+	while (fl == 0.0) {
+		fll = fla;
+		fla = fla + 1111e28;
+		fl = (fl + fla) - fla;
+	}
+
+	printf("`float` maximum: %e\n", fll);
+
+	fl = 0.0;
+	fll = 0.0;
+	fla = 0.0;
+	while (fl == 0.0) {
+		fll = fla;
+		fla = fla - 1111e28;
+		fl = (fl - fla) + fla;
+	}
+
+	printf("`float` minimum: %e\n", fll);
+
+	/* Doubles */
+	while (db == 0.0) {
+		dbl = dba;
+		dba = dba + 1111e297;
+		db = (db + dba) - dba;
+	}
+
+	printf("`float` maximum: %e\n", dbl);
+	printf("`float` minimum: -%e\n", dbl);
+	
+	printf("\nNow, let's cheat and use the helpful headers!\n");
+	printf("`char`s go from %d to %d (unsigned, up to %u)\n", SCHAR_MIN, SCHAR_MAX, UCHAR_MAX);
+	printf("`short`s go from %d to %d (unsigned, up to %u)\n", SHRT_MIN, SHRT_MAX, USHRT_MAX);
+	printf("`int`s go from %d to %d (unsigned, up to %u)\n", INT_MIN, INT_MAX, UINT_MAX);
+	printf("`long`s go from %ld to %ld (unsigned, up to %lu)\n", LONG_MIN, LONG_MAX, ULONG_MAX);
+	printf("`float`s range from %e to %e\n", FLT_MIN, FLT_MAX);
+	printf("`double`s range from %e to %e\n", DBL_MIN, DBL_MAX);
+	return 0;
+}