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authorzlg <zlg@zlg.space>2013-08-19 02:35:49 -0500
committerzlg <zlg@zlg.space>2013-08-19 02:35:49 -0500
commit8bb191cb2808968db87ce39d45f40c1996690553 (patch)
tree82aad6a842d64add93cb01d2cef9a77dfeceaaac
parentSolve Exercise 5-1: fixed getint() (diff)
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Solve Exercise 5-2: getfloat()
-rw-r--r--ch5/5-02_getfloat.c75
1 files changed, 75 insertions, 0 deletions
diff --git a/ch5/5-02_getfloat.c b/ch5/5-02_getfloat.c
new file mode 100644
index 0000000..e6f3347
--- /dev/null
+++ b/ch5/5-02_getfloat.c
@@ -0,0 +1,75 @@
+#include <stdio.h>
+#include <math.h>
+
+/* The C Programming Language: 2nd Edition
+ *
+ * Exercise 5-2: Write getfloat, the floating-point analog of getint. What
+ * type does getfloat return as its function value?
+ *
+ * Answer: getfloat should return an integer, since getint's return value is
+ * only important to check its status, not the value type that it's working
+ * with. The only real "gotcha" here is making sure to use getch() after
+ * checking for a decimal point so the resulting loop will actually execute.
+ */
+
+#define BUFSIZE 100
+
+int getch(void);
+void ungetch(int);
+int getfloat(double *);
+
+char buf[BUFSIZE];
+int bufp = 0;
+
+int main() {
+ double foo;
+ double *bar = &foo;
+ while (getfloat(bar) > 0) {
+ printf("%f\n", foo);
+ }
+ return 0;
+}
+
+int getfloat(double *pn) {
+ int c, sign, places;
+
+ while (isspace(c = getch())) {
+ }
+ if (!isdigit(c) && c != EOF && c != '+' && c != '-') {
+ ungetch(c);
+ return 0;
+ }
+ sign = (c == '-') ? -1 : 1;
+ if (c == '+' || c == '-') {
+ c = getch();
+ }
+ if (c != '.' && !isdigit(c)) {
+ return 0;
+ }
+ for (*pn = 0.0; isdigit(c); c = getch()) {
+ *pn = 10.0 * *pn + (c - '0');
+ }
+ if (c == '.') {
+ c = getch(); // skip the decimal point or the loop won't trigger
+ for (places = -1; isdigit(c); c = getch()) {
+ *pn += (double)(c - '0') * pow(10, places--);
+ }
+ }
+ *pn *= sign;
+ if (c != EOF) {
+ ungetch(c);
+ }
+ return c;
+}
+
+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;
+ }
+}