1 files changed, 59 insertions, 0 deletions
diff --git a/four/atof.c b/four/atof.c
new file mode 100644
index 0000000..86bd651
--- /dev/null
+++ b/four/atof.c
@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <math.h>
+
+#define MAXLINE 128
+
+int
+get_line(char s[], int lim)
+{
+	int c, i;
+	i = 0;
+	while (--lim > 0 && (c = getchar()) != EOF && c != '\n') {
+		s[i++] = c;
+	}
+	if (c == '\n') {
+		s[i++] = c;
+	}
+	s[i] = '\0';
+	return i;
+}
+
+/* convert string to double-precision floating point */
+double
+atof(char s[])
+{
+	double val, power;
+	int i, sign;
+	for (i = 0; isspace(s[i]); ++i);
+	sign = (s[i] == '-') ? -1 : 1;
+	if (s[i] == '+' || s[i] == '-') {
+		++i;
+	}
+	for (val = 0.0; isdigit(s[i]); ++i) {
+		val = 10.0 * val + (s[i] - '0');
+	}
+	if (s[i] == '.') {
+		++i;
+	}
+	for (power = 1.0; isdigit(s[i]); ++i) {
+		val = 10.0 * val + (s[i] - '0');
+		power *= 10.0;
+	}
+	if (s[i] == 'e' || s[i] == 'E') {
+		return sign * val / power * pow(10, s[++i] - '0');
+	}
+	return sign * val / power;
+}
+
+int
+main()
+{
+	double sum;
+	char line[MAXLINE];
+	sum = 0;
+	while (get_line(line, MAXLINE) > 0) {
+		printf("\t%g\n", sum += atof(line));
+	}
+	return 0;
+}