5.2

1 files changed, 73 insertions, 0 deletions

diff --git a/5/2.c b/5/2.c
new file mode 100644
index 0000000..db37319
--- /dev/null
+++ b/5/2.c
@@ -0,0 +1,73 @@
+#include <ctype.h>
+#include <stdio.h>
+
+#define BUFSIZE 100
+
+int getfloat(float *);
+
+int main(int argc, char *argv[]) {
+  int rc;
+  float f;
+
+  while ((rc = getfloat(&f)) != EOF && rc != 0)
+    printf("\t%.8g\n", f);
+
+  if (rc == 0)
+    printf("error: not a valid number\n");
+
+  return 0;
+}
+
+char buf[BUFSIZE];
+int bufp = 0;
+
+int getch() { return (bufp > 0) ? buf[--bufp] : getchar(); }
+
+void ungetch(int c) {
+  if (bufp >= BUFSIZE)
+    printf("ungetch: too many characters\n");
+  else
+    buf[bufp++] = c;
+}
+
+int getfloat(float *pf) {
+  int c, sign, rad, div;
+
+  rad = 0;
+
+  while (isspace(c = getch()))
+    ;
+
+  if (!isdigit(c) && c != EOF && c != '+' && c != '-' && c != '.') {
+    ungetch(c);
+    return 0;
+  }
+
+  sign = (c == '-') ? -1 : 1;
+
+  if ((c == '+' || c == '-') && !isdigit(c = getch()) && c != '.') {
+    ungetch(c);
+    return 0;
+  }
+
+  for (*pf = 0.0, div = 1.0; isdigit(c) || c == '.'; c = getch()) {
+    if (c == '.') {
+      if (rad > 0)
+        return 0;
+      rad++;
+      continue;
+    }
+
+    if (rad)
+      div *= 10;
+
+    *pf = 10.0 * *pf + (c - '0');
+  }
+
+  *pf = (sign * *pf) / div;
+
+  if (c != EOF)
+    ungetch(c);
+
+  return c;
+}
\ No newline at end of file