1 files changed, 157 insertions, 0 deletions
diff --git a/5.18.c b/5.18.c
new file mode 100644
index 0000000..4e8f13a
--- /dev/null
+++ b/5.18.c
@@ -0,0 +1,157 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+#define MAXTOKEN	100
+#define OUTLEN		1000
+#define MAXBUFF		100
+
+enum { NAME, PARENS, BRACKETS };
+enum { NO, YES };
+
+void err(char *s);
+void errmsg(char *s);
+
+void dcl(void);
+void dirdcl(void);
+
+int gettoken(void);
+int tokentype;
+int prevtoken;
+char token[MAXTOKEN];
+char name[MAXTOKEN];
+char datatype[MAXTOKEN];
+char out[OUTLEN];
+
+char buff[MAXBUFF];
+static size_t top;
+
+void errmsg(char *s)
+{
+	printf("err: %s\n", s);
+	prevtoken = YES;
+}
+
+void err(char *s)
+{
+	printf("fatal error: %s\n", s);
+	exit(1);
+}
+
+void dcl(void)
+{
+	int ns;
+
+	for (ns = 0; gettoken() == '*';)
+		ns++;
+	dirdcl();
+	while (ns-- > 0)
+		strcat(out, " pointer to");
+}
+
+void dirdcl(void)
+{
+	int type;
+
+	if (tokentype == '(') {
+		dcl();
+		if (tokentype != ')')
+			errmsg("missing )");
+	} else if (tokentype == NAME) {
+		strcpy(name, token);
+	} else {
+		errmsg("expected name or (dcl)");
+	}
+
+	while ((type = gettoken()) == PARENS || type == BRACKETS) {
+		if (type == PARENS) {
+			strcat(out, " function returning");
+		} else {
+			strcat(out, " array");
+			strcat(out, token);
+			strcat(out, " of");
+		}
+	}
+}
+
+int gettoken(void)
+{
+	char c, *p = token;
+	char getch(void);
+	void ungetch(char);
+
+	if (prevtoken == YES) {
+		prevtoken = NO;
+		return tokentype;
+	}
+
+	while(isblank(c = getch()))
+		;
+
+	if (c == '/') { /* ignore comments */
+		if ((c = getch()) == '/') {
+			while ((c = getch()) != '\n')
+				;
+		} else if (c == '*') {
+			while (getch() != '*' || (c = getch()) != '/')
+				if (c == '*')
+					ungetch('*');
+			return gettoken();
+		} else {
+			ungetch(c);
+			c = '/';
+		}
+	}
+
+	if (c == '(') {
+		if ((c = getch()) == ')') {
+			strcpy(token, "()");
+			return tokentype = PARENS;
+		} else {
+			ungetch(c);
+			return tokentype = '(';
+		}
+	} else if (c == '[') {
+		for (*p++ = '['; (*p++ = getch()) != ']';)
+			;
+		*p = '\0';
+		return tokentype = BRACKETS;
+	} else if (isalpha(c)) {
+		for (*p++ = c; isalnum(c = getch());)
+			*p++ = c;
+		*p = '\0';
+		ungetch(c);
+		return tokentype = NAME;
+	} else {
+		return tokentype = c;
+	}
+}
+
+void ungetch(char c)
+{
+	if (top < MAXBUFF)
+		buff[top++] = c;
+	else
+		err("stack overflow");
+}
+
+char getch(void)
+{
+	return (top > 0) ? buff[--top] : getchar();
+}
+
+int main(void)
+{
+	while (gettoken() != EOF) {
+		if (tokentype == '\n') /* skip empty lines */
+			continue;
+		strcpy(datatype, token);
+		out[0] = '\0';
+		dcl();
+		if (tokentype != '\n')
+			printf("synatx error\n");
+		printf("%s: %s %s\n", name, out, datatype);
+	}
+	return 0;
+}