Recursive descent analysis-Experimental report

First, Experimental Purpose

Compile a recursive descent analysis program.

E→te '

E ' → (+t|-t) e ' |ε

T→ft '

T ' → (*f|/f) t ' |ε

f→ (E) |i

Second, experimental content and requirements

Input: an arithmetic expression;

Judge: Each encounter a terminator, then determine whether the current read word symbol is matched with the Terminator, if matched, continue to read the next word symbol, if not match, then error processing.

Each non-Terminator is encountered, the corresponding parser subroutine is called

Test methods, steps and Results

1. SOURCE program Name: recursive descent analysis. C

executable name: recursive descent parsing. exe

#include <stdio.h>
#include <string.h>
void Scaner ();
Error ();
E ();
E1 ();
T ();
T1 ();
F ();
Char character[80];//holds all the input characters
Char token[8];//Word itself string
Char ch;//single character
int p,m=0,i,sum=0,syn;//sum: integer constant row: Record the line number of the newly read-in Word lines, syn: Word species code
Char *keywords[6]={' begin ', ' if ', ' then ', ' while ', ' Do ', ' end '};
void Main () {
P=0;
printf ("Please enter a string:");
Do
{
Ch=getchar ();
Character[i++]=ch;
}while (ch!= ' # ');//Enter with the # key to end
P=0;
Do
{
Scaner ();//Recognize words
Switch (SYN)
{
Case 11:printf ("(%d,%d) \ n", syn,sum);
Case-1: printf ("(%s,#) \ n", token);
Default:printf ("(%d,%s) \ n", Syn,token);
}
}while (syn!=0);
P=0;
Scaner ();
E ();
if (syn==0)
printf ("success!\n");
Else
printf ("failure!\n");
}
Lexical analysis Program
void Scaner ()
{
for (i=0;i<8;i++)
Token[i]=null;
Ch=character[p++];
while (ch== ")
{
CH=CHARACTER[P];
p++;
}
if ((ch>= ' a ' &&ch<= ' z ') | | (ch>= ' A ' &&ch<= ' Z ')) Identifier or variable name
{
m=0;
while ((ch>= ' 0 ' &&ch<= ' 9 ') | | (ch>= ' A ' &&ch<= ' z ') | | (ch>= ' A ' &&ch<= ' Z '))
{
Token[m++]=ch;
Ch=character[p++];
}
token[m++]= ' + ';
p--;
syn=10;
for (i=0;i<6;i++)//Compare the identified characters with the defined identifiers,
if (strcmp (Token,keywords[i]) ==0)
{
syn=i+1;
Break
}
}
else if ((ch>= ' 0 ' &&ch<= ' 9 '))//Digital
{
sum=0;
while ((ch>= ' 0 ' &&ch<= ' 9 '))
{
sum=sum*10+ (ch-' 0 ');
Ch=character[p++];

}
syn=11;
p--;
}
else switch (CH)//Other characters
{
Case ' < ': m=0;token[m++]=ch;
Ch=character[p++];
if (ch== ' = ')
{
syn=21;
Token[m++]=ch;
}
else if (ch== ' > ')
{
syn=22;
Token[m++]=ch;
}
Else
{
syn=23;
p--;
}
Break
Case ' > ': m=0;token[m++]=ch;
Ch=character[p++];
if (ch== ' = ')
{
syn=24;
Token[m++]=ch;
}
Else
{
syn=20;
p--;
}
Break
Case ': ': m=0;token[m++]=ch;
Ch=character[p++];
if (ch== ' = ')
{
syn=18;
Token[m++]=ch;
}
Else
{
syn=17;
p--;
}
Break
Case ' + ': syn=13;token[0]=ch;break;
Case '-': syn=14;token[0]=ch;break;
Case ' * ': syn=15;token[0]=ch;break;
Case '/': syn=16;token[0]=ch;break;
Case ' = ': syn=25;token[0]=ch;break;
Case '; ': syn=26;token[0]=ch;break;
Case ' (': syn=27;token[0]=ch;break;
Case ') ': syn=28;token[0]=ch;break;
Case ' # ': syn=0;token[0]=ch;break;
Default:syn=-1;break;

}
}
Error ()
{
printf ("(%d,%s) failure! \ n ", syn, token);
}
E ()
{
T ();
E1 ();
}
E1 ()
{
if (syn==13| | SYN==14)
{
Scaner ();
T ();
E1 ();
}

}
T ()
{
F ();
T1 ();
}
T1 ()
{
if (syn==15| | SYN==16)
{
Scaner ();
F ();
T1 ();
}else if (syn!=28 && syn!=0 && syn!=13 && syn!=14)
Error ();

}
F ()
{
if (syn==27)
{
Scaner ();
E ();
if (syn==28)
Scaner ();
else error ();
}
else if (syn==10| | SYN==11)
Scaner ();
}

Recursive descent analysis-Experimental report