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satyajitghanasatyajitghana
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added Exercise 5-18
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6 files changed

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‎Chapter-5/Exercise 5-18/buffer.c

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#include <stdio.h>
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#include <string.h>
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#define BUFSIZE 100
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int buf[BUFSIZE]; /* buffer for ungetch */
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int bufp = 0; /* buffer pointer (not a real pointer) */
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int getch(void) /* get a (possibly pushed back) character */ {
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return (bufp > 0) ? buf[--bufp] : getchar();
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}
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void ungetch(int c) /* push character back on input */ {
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if (bufp >= BUFSIZE)
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printf("ungetch : too many characters\n");
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else
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buf[bufp++] = c;
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}
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void ungets(char s[]) /* push string s back to input */ {
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int i = strlen(s);
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while (i > 0) ungetch(s[--i]);
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}

‎Chapter-5/Exercise 5-18/buffer.h

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#ifndef BUFFER_H
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#define BUFFER_H
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int getch(void);
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void ungetch(int);
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void ungets(char []);
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#endif

‎Chapter-5/Exercise 5-18/main.c

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#include <stdio.h>
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#include <string.h>
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#include <ctype.h>
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#include "buffer.h"
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#define MAXTOKEN 100
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enum { NAME, PARENS, BRACKETS };
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void dcl(void);
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void dirdcl(void);
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int gettoken(void);
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int tokentype; /* type of last token */
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char token[MAXTOKEN]; /* last token string */
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char name[MAXTOKEN]; /* indetifier name */
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char datatype[MAXTOKEN]; /* data type = char, int, etc. */
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char out[1024]; /* output string */
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int main() {
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while (gettoken() != EOF) { /* 1st token on line */
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strcpy(datatype, token); /* is the datatype */
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out[0] = '\0';
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dcl(); /* parse rest of the line */
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if (tokentype != '\n')
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printf("syntax error\n");
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printf("%s: %s %s\n", name, out, datatype);
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}
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return 0;
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}
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/* dcl: parse a declarator */
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void dcl(void) {
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int ns;
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for (ns = 0; gettoken() == '*'; ) /* count *'s */
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ns++;
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dirdcl();
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while (ns-- > 0)
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strcat(out, " pointer to");
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}
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/* dirdcl: parse a direct declarator */
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void dirdcl(void) {
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int type;
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if (tokentype == '(') { /* ( dcl ) */
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dcl();
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if (tokentype != ')')
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printf("error: missing )\n");
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} else if (tokentype == NAME) /* variable name */
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strcpy(name, token);
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else
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printf("error: expected name or (dcl)\n");
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while ((type = gettoken()) == PARENS || type == BRACKETS)
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if (type == PARENS)
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strcat(out, " function returning");
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else {
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strcat(out, " array");
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strcat(out, token);
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strcat(out, " of");
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}
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}
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int gettoken(void) /* return next token */ {
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int c, getch(void);
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void ungetch(int);
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char *p = token;
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while((c = getch()) == ' ' || c == '\t')
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;
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if (c == '(') {
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if ((c = getch()) == ')') {
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strcpy(token, "()");
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return tokentype = PARENS;
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} else {
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ungetch(c);
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return tokentype = '(';
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}
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} else if (c == '[') {
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for (*p++ = c; (*p++ = getch()) != ']'; )
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;
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*p = '\0';
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return tokentype = BRACKETS;
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} else if (isalpha(c)) {
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for (*p++ = c; isalnum(c = getch()); )
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*p++ = c;
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*p = '\0';
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ungetch(c);
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return tokentype = NAME;
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} else
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return tokentype = c;
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}

‎Chapter-5/dcl/buffer.c

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#include <stdio.h>
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#include <string.h>
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#define BUFSIZE 100
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int buf[BUFSIZE]; /* buffer for ungetch */
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int bufp = 0; /* buffer pointer (not a real pointer) */
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int getch(void) /* get a (possibly pushed back) character */ {
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return (bufp > 0) ? buf[--bufp] : getchar();
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}
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void ungetch(int c) /* push character back on input */ {
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if (bufp >= BUFSIZE)
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printf("ungetch : too many characters\n");
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else
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buf[bufp++] = c;
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}
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void ungets(char s[]) /* push string s back to input */ {
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int i = strlen(s);
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while (i > 0) ungetch(s[--i]);
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}

‎Chapter-5/dcl/buffer.h

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#ifndef BUFFER_H
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#define BUFFER_H
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int getch(void);
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void ungetch(int);
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void ungets(char []);
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#endif

‎Chapter-5/dcl/main.c

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#include <stdio.h>
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#include <string.h>
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#include <ctype.h>
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#define MAXTOKEN 100
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enum { NAME, PARENS, BRACKETS };
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void dcl(void);
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void dirdcl(void);
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int gettoken(void);
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int tokentype; /* type of last token */
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char token[MAXTOKEN]; /* last token string */
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char name[MAXTOKEN]; /* indetifier name */
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char datatype[MAXTOKEN]; /* data type = char, int, etc. */
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char out[1024]; /* output string */
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int main() {
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while (gettoken() != EOF) { /* 1st token on line */
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strcpy(datatype, token); /* is the datatype */
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out[0] = '\0';
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dcl(); /* parse rest of the line */
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if (tokentype != '\n')
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printf("syntax error\n");
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printf("%s: %s %s\n", name, out, datatype);
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}
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return 0;
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}
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/* dcl: parse a declarator */
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void dcl(void) {
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int ns;
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for (ns = 0; gettoken() == '*'; ) /* count *'s */
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ns++;
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dirdcl();
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while (ns-- > 0)
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strcat(out, " pointer to");
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}
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/* dirdcl: parse a direct declarator */
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void dirdcl(void) {
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int type;
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if (tokentype == '(') { /* ( dcl ) */
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dcl();
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if (tokentype != ')')
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printf("error: missing )\n");
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} else if (tokentype == NAME) /* variable name */
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strcpy(name, token);
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else
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printf("error: expected name or (dcl)\n");
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while ((type = gettoken()) == PARENS || type == BRACKETS)
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if (type == PARENS)
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strcat(out, " function returning");
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else {
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strcat(out, " array");
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strcat(out, token);
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strcat(out, " of");
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}
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}
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int gettoken(void) /* return next token */ {
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int c, getch(void);
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void ungetch(int);
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char *p = token;
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while((c = getch()) == ' ' || c == '\t')
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;
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if (c == '(') {
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if ((c = getch()) == ')') {
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strcpy(token, "()");
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return tokentype = PARENS;
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} else {
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ungetch(c);
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return tokentype = '(';
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}
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} else if (c == '[') {
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for (*p++ = c; (*p++ = getch()) != ']'; )
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;
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*p = '\0';
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return tokentype = BRACKETS;
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} else if (isalpha(c)) {
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for (*p++ = c; isalnum(c = getch()); )
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*p++ = c;
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*p = '\0';
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ungetch(c);
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return tokentype = NAME;
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} else
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return tokentype = c;
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}

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