无符号数词法分析程序

#include <stdio.h>
#include <ctype.h>
#include <math.h>
#define DIGIT 1
#define POINT 2
#define OTHER 3
#define POWER 4
#define PLUS 5
#define MINUS 6
#define UCON 7 //Suppose the class number of unsigned constant is 7
#define ClassOther 200
#define EndState -1
int w,n,p,e,d;
int Class; //Used to indicate class of the word
int ICON;
float FCON;
static int CurrentState; //Used to present current state, the initial value:0
int GetChar (void);
int EXCUTE (int,int);
int LEX (void);
//_____________________________________________________________________________ _________________________
int HandleOtherWord (void)
{
return ClassOther;
}
//_____________________________________________________________________________ __________________________
int HandleError (void)
{printf ("Error!\n"); return 0;}
//_____________________________________________________________________________ __________________________
int GetChar (void)
{
int c;
c=getchar( );
if(isdigit(c)) {d=c-'0';return DIGIT;}
if (c=='.') return POINT;
if (c=='E'||c=='e') return POWER;
if (c=='+') return PLUS;
if (c=='-') return MINUS;
return OTHER;
}
//_____________________________________________________________________________ ___________________________
int EXCUTE (int state, int symbol)
{
switch(state)
{
case 0:switch (symbol)
{
case DIGIT: n=0;p=0;e=1;w=d;CurrentState=1;Class=UCON;break;
case POINT: w=0;n=0;p=0;e=1;CurrentState=3;Class=UCON;break;
default: HandleOtherWord( );Class=ClassOther;
CurrentState=EndState;
}
break;
case 1:switch (symbol)
{
case DIGIT: w=w*10+d;break; //CurrentState=1
case POINT: CurrentState=2;break;
case POWER: CurrentState=4;break;
default: ICON=w;CurrentState=EndState;
}
break;
case 2:switch (symbol)
{
case DIGIT: n++;w=w*10+d;break;
case POWER: CurrentState=4;break;
default: FCON=w*pow(10,e*p-n) ;CurrentState=EndState;
}
break;
case 3:switch (symbol)
{
case DIGIT: n++;w=w*10+d;CurrentState=2;break;
default: HandleError( );CurrentState=EndState;
}
break;
case 4:switch (symbol)
{
case DIGIT: p=p*10+d;CurrentState=6;break;
case PLUS: CurrentState=5;break;
default: HandleError( );CurrentState=EndState;
}
break;
case 5:switch (symbol)
{
case DIGIT: p=p*10+d;CurrentState=6;break;
default: HandleError( );CurrentState=EndState;
}
break;
case 6:switch (symbol)
{
case DIGIT: p=p*10+d;break;
default:
FCON=w*pow(10,e*p-n);
CurrentState=EndState;
}
break;
}
return CurrentState;
}
//_____________________________________________________________________________ ______________________________
int LEX (void)
{
int ch;
CurrentState=0;
while (CurrentState!=EndState)
{
ch= GetChar();
EXCUTE (CurrentState,ch);
}
return Class;
}
int main()
{
int c =LEX();
printf("%d\n",c);
printf("%lf\n",FCON);
}。