feat: solve 5-2

chapter-5/5-2.c

@@ -0,0 +1,45 @@
+#include <ctype.h>
+#include <stdio.h>
+#define SIZE 100
+
+int getfloat(double *pf) {
+  int c, sign, dec;
+  while (isspace(c = getchar())) /* ignore whitespace */
+    ;
+  if (c != EOF && c != '.' && c != '+' && c != '-' && !isdigit(c)) {
+    ungetc(c, stdin); // not a number
+    return c;
+  }
+  sign = (c == '-') ? -1 : 1;
+  if (c == '+' || c == '-')
+    c = getchar();
+
+  for (*pf = 0; isdigit(c); c = getchar()) {
+    *pf = 10 * *pf + (c - '0');
+  }
+
+  if (c != '.' && c != EOF) {
+    ungetc(c, stdin); // not a number after decimal
+    return c;
+  }
+
+  if (c == '.') {
+    c = getchar();
+    for (dec = 1; isdigit(c); c = getchar(), dec++)
+      *pf = *pf + (double)(c - '0') / (10 * dec);
+  }
+
+  *pf *= sign;
+
+  if (c != EOF)
+    ungetc(c, stdin);
+  return c;
+}
+
+int main() {
+  int n;
+  double array[SIZE];
+  for (n = 0; n < SIZE && getfloat(&array[n]) != EOF; n++)
+    ;
+  printf("%lf", array[0]);
+}