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-rw-r--r--pl_calc.c101
1 files changed, 101 insertions, 0 deletions
diff --git a/pl_calc.c b/pl_calc.c
new file mode 100644
index 0000000..9a93ebe
--- /dev/null
+++ b/pl_calc.c
@@ -0,0 +1,101 @@
+/* $Id$ */
+/* Berlin 26.12.2000 */
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#define MAXOP 100
+#define NUMBER '0'
+#define MAXVAL 100
+#define BUFSIZE 100
+
+int getop(char[]);
+void push(double);
+double pop(void);
+
+int sp = 0;
+double val[MAXVAL];
+int getch(void);
+void ungetch(int);
+char buf[BUFSIZE];
+int bufp = 0;
+
+int main(void) {
+ int type;
+ double op2;
+ char s[MAXOP];
+ while ((type = getop(s)) != EOF) {
+ switch (type) {
+ case NUMBER:
+ push(atof(s));
+ break;
+ case '+':
+ push(pop() + pop());
+ break;
+ case '*':
+ push(pop() * pop());
+ break;
+ case '-':
+ op2 = pop();
+ push(pop() - op2);
+ break;
+ case '/':
+ op2 = pop();
+ if (op2 != 0.0)
+ push(pop() / op2);
+ else
+ printf("Fehler: Teilung durch Null\n");
+ break;
+ case '\n':
+ printf("\t%.8g\n", pop());
+ break;
+ default:
+ printf("Fehler: Unbekanter Befehl %s\n", s);
+ break;
+ }
+ }
+ return 0;
+}
+
+void push(double f) {
+ if (sp < MAXVAL)
+ val[sp++] = f;
+ else
+ printf("Fehler: Stack ist voll, %g passt nicht rein\n", f);
+}
+
+double pop(void) {
+ if (sp > 0)
+ return val[--sp];
+ else {
+ printf("Fehler: Stack ist leer\n");
+ return 0.0;
+ }
+}
+
+int getop(char s[]) {
+ int i, c;
+ while((s[0] = c = getch()) == ' ' || c == '\t');
+ s[1] = '\0';
+ if (!isdigit(c) && c != '.')
+ return c;
+ i = 0;
+ if (isdigit(c))
+ while (isdigit(s[++i] = c = getch()));
+ if (c == '.')
+ while (isdigit(s[++i] = c = getch()));
+ s[i] = '\0';
+ if (c != EOF)
+ ungetch(c);
+ return NUMBER;
+}
+
+int getch(void) {
+ return(bufp > 0) ? buf[--bufp] : getchar();
+}
+
+void ungetch(int c) {
+ if (bufp >= BUFSIZE)
+ printf("Ungetch: Zu viele Zeichen\n");
+ else
+ buf[bufp++] = c;
+}