Định danh biểu thức hậu tố.

program Hau_to;
uses crt;
Type
    mang=array[1..1000]of string[10];
    mang1=array[1..1000] of real;
var bthuc:mang;
    s:mang1;
    i,n,kt,T:integer;
    x,y,z,w:real;
procedure Push(var S:mang1;var T:integer; X:real);
   begin
        if (T>=n) then
           writeln('Tran STACK.')
        else
            begin
              inc(t);
              s[T]:=x;
            end;
        textcolor(red);
        writeln('Da day so ',x:2:2,' vao STACK.');
        textcolor(white);
   End;
Function Pop(S:mang1;var T:integer):real;
   begin
        if T<=0 then
           writeln('STACK het.')
        else
          begin
               Pop:=s[t];
               textcolor(blue);
               writeln('  Lay ',s[t]:2:2,' ra khoi STACK.');
               textcolor(white);
               dec(t);
          end;

   End;
Procedure Nhap;
   begin
        i:=0;
        textcolor(green);
        writeln('Nhap tung phan tu cua bieu thuc.');
        writeln('Nhap # de ket thuc bieu thuc.');
        textcolor(white);
        writeln;
        repeat
              inc(i);
              write('Nhap phan tu: ');
              readln(bthuc[i]);
        until bthuc[i]='#';
        n:=i;
   end;
Begin
     clrscr;
     Nhap;
     for i:=1 to n-1  do
         write(bthuc[i],' ');
     i:=1;
     writeln;
     t:=0;
     Repeat
           val(bthuc[i],x,kt);
           if kt=0 then
                   push(s,t,x)

           else
               begin
                  y:=Pop(S,t);
                  z:=Pop(S,t);
                  textcolor(yellow);
                  if bthuc[i]='+' then
                     begin
                        writeln('Thuc hien phep toan ',z:2:2,bthuc[i],y:2:2,'=',z+y:2:2);
                        w:=y+z;
                     end;
                  if bthuc[i]='-' then
                     begin
                        writeln('Thuc hien phep toan ',z:2:2,bthuc[i],y:2:2,'=',z-y:2:2);
                        w:=z-y;
                     end;
                  if bthuc[i]='*' then
                     begin
                        writeln('Thuc hien phep toan ',z:2:2,bthuc[i],y:2:2,'=',z*y:2:2);
                        w:=z*y;
                     end;
                  if bthuc[i]='/' then
                     begin
                        writeln('Thuc hien phep toan ',z:2:2,bthuc[i],y:2:2,'=',z/y:2:2);
                        w:=z/y;
                     end;
                  textcolor(white);
                  delay(1250);
                  Push(s,t,w);
               end;
           inc(i);
     until bthuc[i]='#';
     textcolor(green);
     writeln;
     write('Dinh gia cua bieu thuc = ',w:4:2);
     readln
End.