Experimental study of three Recursive descent analysis program

First, Experimental Purpose

compile a recursive descent analysis program.

Second, experimental content and requirements

Input: Normal type

Output: Determine if the normal formula is correct.

Third, test methods, procedures and results

1. source program name: Recursive descent analysis program . C

executable name: Recursive descent analysis program . EXE

2.

3. main procedural paragraphs and their explanations:

#include <stdio.h> #include <string> char str[50]; int index=0;                void E (); e->tx;                void X (); X->+tx |                e void T ();                t->fy void Y (); Y->*fy |                e void F (); F-> (E) |     I int main ()/* recursive parsing */{int len;     int m;     printf ("Please enter the number of times to test:");     scanf ("%d", &m);         while (m--) {printf ("Please enter string (length <50>): \ n");        scanf ("%s", str);        Len=strlen (str);        str[len]= ' # ';         str[len+1]= ' + ';         E ();         printf ("%s is a valid symbolic string!\n", str);         strcpy (str, "");    index=0; } return 0;    } void E () {T (); X ();}         void X () {if (str[index]== ' + ') {index++;         T ();     X ();     }} void T () {F (); Y ();         } void Y () {if (str[index]== ' * ') {index++;         F ();     Y ();     }} void F () {if (str[index]== ' I ') {index++;}         else if (str[index]== ' (') {index++; E); if (str[index]== ') ') {index++;}            else {printf ("\ nthe illegal symbolic string!\n");         Exit (0);         }} else {printf ("illegal symbol string!\n");     Exit (0); } }

4.operational results and analysis

Four, Experimental Summary

Through this experiment, for recursion and have a new understanding of the work principle is further mastered. This experiment has helped me a lot.

Experimental study of three Recursive descent analysis program