Finished exercise 5.2

ch_05/exercise_05-02/main.c

@@ -0,0 +1,106 @@
+/*
+ *
+ * Exercise 5-2. Write getfloat, the floating-point analog of getint. What type does getfloat
+ * return as its function value?
+ *
+ * Author: Kun Deng
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+
+#define BUFSIZE 100
+#define SIZE 1024
+
+int getch(void);
+void ungetch(int);
+
+int getfloat(float *ptr);
+
+
+int main(void)
+{
+    int n;
+    float array[SIZE];
+
+    for(n=0; n<SIZE && getfloat(&array[n]) != EOF; n++)
+        ;
+
+    for(; n >= 0; n--)
+    {
+        printf("%f ",array[n]);
+    }
+
+    printf("\n");
+
+    return 0;
+}
+
+int getfloat(float *ptr)
+{
+    int c,sign;
+    float power;
+
+    while(isspace(c = getch()))
+        ;
+
+    if(!isdigit(c) && c != EOF && c != '+' && c != '-' && c != '.')
+    {
+        ungetch(c);
+        return 0;
+    }
+
+    sign = (c == '-') ? -1: 1;
+
+    if(c == '+' || c == '-')
+    {
+        c = getch();
+    }
+
+    for(*ptr = 0.0; isdigit(c); c = getch())
+    {
+        *ptr = 10.0 * (*ptr) + (c - '0');
+    }
+
+    if(c == '.')
+    {
+        c = getch();
+    }
+
+    for(power=1.0; isdigit(c); c = getch())
+    {
+        *ptr = 10.0 * (*ptr) + (c - '0');   /* fractional part */
+        power *= 10.0;
+    }
+
+    *ptr  *= sign / power;
+
+    if(c != EOF)
+    {
+        ungetch(c);
+    }
+
+    return c;
+}
+
+char buf[BUFSIZE];
+int bufp = 0;
+
+int getch(void)
+{
+    return (bufp > 0) ? buf[--bufp] : getchar();
+}
+
+void ungetch(int c)
+{
+    if(bufp >= BUFSIZE)
+    {
+        printf("ungetch: too many characters\n");
+    }
+    else
+    {
+        buf[bufp++] = c;
+    }
+}