1 files changed, 35 insertions, 0 deletions
diff --git a/four/getop.c b/four/getop.c
new file mode 100644
index 0000000..8870895
--- /dev/null
+++ b/four/getop.c
@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <ctype.h>
+
+#define NUMBER '0'
+
+int getch(void);
+void ungetch(int);
+
+/* get next operator or numeric operand */
+int
+getop(char s[])
+{
+	int i, c;
+
+	while((s[0] = c = getch()) == ' ' || c == '\t');
+	s[1] = '\0';
+	/* not a number */
+	if (!isdigit(c) && c != '.') {
+		return c;
+	}
+	i = 0;
+	/* collect integer part */
+	if (isdigit(c)) {
+		while (isdigit(s[++i] = c = getch()));
+	}
+	/* collect fraction part */
+	if (c == '.') {
+		while (isdigit(s[++i] = c = getch()));
+	}
+	s[i] = '\0';
+	if (c != EOF) {
+		ungetch(c);
+	}
+	return NUMBER;
+}