5.6

1 files changed, 80 insertions, 0 deletions

diff --git a/5.6.1.c b/5.6.1.c
new file mode 100644
index 0000000..1810198
--- /dev/null
+++ b/5.6.1.c
@@ -0,0 +1,80 @@
+#include <stdio.h>
+#include <ctype.h>
+
+#define MAXLEN 64
+
+int sneed_getline(char str[], int max);
+double atof(const char str[]);
+
+int 
+main(void)
+{
+  char str[MAXLEN];
+
+  while (sneed_getline(str, MAXLEN) > 0)
+    printf("%f\n\n", atof(str));
+
+  return 0;
+}
+
+int
+sneed_getline(char str[], int max)
+{
+  char input;
+  char *str_og = str;
+
+  while (--max && (*str = input = getchar()) != EOF && input != '\n')
+    str++;
+
+  if (!max && input != '\n')
+    *str = '\n', str++;
+
+  str = '\0';
+
+  return str - str_og;
+}
+
+double 
+atof(const char str[])
+{
+  int i, sign, e_sign, j;
+  double val, power, e_power;
+
+  for (i = 0; isspace(str[i]); i++)
+    ;
+  sign = (str[i] == '-') ? -1 : 1;
+
+  if (str[i] == '-' || str[i] == '+')
+    i++;
+
+  for(val = 0.0; isdigit(str[i]); i++)
+    val = val * 10.0 + (str[i] - '0');
+
+  if (str[i] == '.')
+    i++;
+
+  for(power = 1.0; isdigit(str[i]); i++) {
+    val = 10 * val + (str[i] - '0');
+    power *= 10.0;
+  }
+
+  if (str[i] == 'e' || str[i] == 'E')
+    i++;
+
+  e_sign = (str[i] == '-') ? -1 : 1;
+
+  if (str[i] == '-' || str[i] == '+')
+    i++;
+
+  for (e_power = 0.0; isdigit(str[i]); i++)
+    e_power = e_power * 10 + (str[i] - '0');
+
+  if (e_sign < 0)
+    for (j = 0; j < e_power; j++)
+      power *= 10.0;
+  else
+    for (j = 0; j < e_power; j++)
+      power /= 10.0;
+
+  return (sign * val / power);
+}