#include<iostream.h>
#include<stdlib.h>
#include<ctype.h>
#include<PROCESS.H>
#include<STRSTREAM.H>
typedef float elemtype;
struct stack
{
elemtype *stack;
short top;
short stackmaxsize;
};
static void initstack ( stack &s,int ms )
{
s.stack=new elemtype[ms];
if ( !s.stack )
{
cerr<<"memory full!"<<endl;
exit ( 1 );
}
s.top=-1;
s.stackmaxsize=ms;
}
static void clearstack ( stack &s )
{ s.top=-1;}
static void deletestack ( stack &s )
{
delete []s.stack;
s.top=-1;
s.stackmaxsize=0;
}
static int stackempty ( stack &s )
{ return s.top==-1;}
static elemtype peek ( stack &s )
{
if ( s.top==-1 )
{
cerr<<"stack empty!"<<endl;
exit ( 1 );
}
return s.stack[s.top];
}
static void push ( stack &s,elemtype itim )
{
if ( s.top==s.stackmaxsize-1 )
{
cerr<<"stack ovflw!"<<endl;
exit ( 1 );
}
s.top++;
s.stack[s.top]=itim;
}
static elemtype pop ( stack &s )
{
if ( s.top==-1 )
{
cerr<<"stack empty!"<<endl;
exit ( 1 );
}
s.top--;
return s.stack[s.top+1];
}
static int stackfull ( stack &s )
{
return s.top==s.stackmaxsize-1;
}
int precedence ( char op )
{
switch ( op )
{
case'+':
case'-':
return 1;
case'*':
case'/':
return 2;
case'(':
case'@':
default:
return 0;
}
}
static float compute ( char *str )
{
typedef float elemtype;
int sm=20;
stack s;
initstack ( s,sm );
istrstream ins ( str );
char ch;
float x;
ins>>ch;
while ( ch!='@' )
{
switch ( ch )
{
case'+':
x=pop ( s ) +pop ( s );
break;
case'-':
x=pop ( s );
x=pop ( s )-x;
break;
case'*':
x=pop ( s ) *pop ( s );
break;
case'/':
x=pop ( s );
if ( x!=0 )
x=pop ( s ) /x;
else
{
cerr<<"divide by 0!"<<endl;
exit ( 1 );
}
break;
default:
ins.putback ( ch );
ins>>x;
}
push ( s,x );
ins>>ch;
}
// x=pop(s);
// return x;
if ( !stackempty ( s ) )
{
x=pop ( s );
if ( !stackempty ( s ) )
{
cerr<<"expression error!"<<endl;
exit ( 1 );
}
}
else
{
cerr<<"stack is empty!"<<endl;
exit ( 1 );
}
return x;
}
static void change ( char *s1,char *s2 )
{
typedef char elemtype;
int ms=20;
stack r;
initstack ( r,ms );
push ( r,'@' );
int i,j;
i=0;
j=0;
char ch=s1[i];
while ( ch!='@' )
{
if ( ch==' ' )
ch=s1[++i];
else if ( ch=='(' )
{
push ( r,ch );
ch=s1[++i];
}
else if ( ch==')' )
{
while ( peek ( r ) !='(' )
s2[j++]=pop ( r );
pop ( r );
ch=s1[++i];
}
else if ( ch=='+'||ch=='-'||ch=='*'||ch=='/' )
{
char w=peek ( r );
while ( precedence ( w ) >=precedence ( ch ) )
{
s2[j++]=w;
pop ( r );
w=peek ( r );
}
push ( r,ch );
ch=s1[++i];
}
else
{
while ( isdigit ( ch ) ||ch=='.' )
{
s2[j++]=ch;
ch=s1[++i];
}
s2[j++]=' ';
}
}
ch=pop ( r );
while ( ch!='@' )
{
if ( ch=='(' )
{
cerr<<"expression error!"<<endl;
exit ( 1 );
}
else
{
s2[j++]=ch;
ch=pop ( r );
}
}
s2[j++]='@';
s2[j++]='\0';
}
void main()
{
char a[50],b[50];
cout<<"input in @ end :"<<endl;
cin.getline ( a,sizeof ( a ) );
change ( a,b );
cout<<"dui ying de hou zhui biao da shi:"<<endl;
cout<<b<<endl;
cout<<"qiu zhi jie guo shi:"
<<compute ( b ) <<endl;
}