test4.txt

PL/0语言编译器的实现

const true =1,false=0;
var x,y,m,n,pf;
procedure prime;
var i,f;
   procedure mod;
     x:=x-x/y*y;
     begin f:=true;
     i:=3;
     while i<m do
        begin x:=m;
          y:=i;
          call mod;
          if x=0 then f:=false;
          i:=i+2;
          end;
     if f = true then
        begin
          write(m);
          pf:=true;
          end;
     end;
     begin
       pf:=false;
       read(n);
       while n>=2 do
       begin
          write(2);
          if n=2 then pf:=true;
          m:=3;
          while m <= n do
              begin call prime;
                  m:=m+2;
              end;
          read(n);
       end;
       if pf =false then write(0);
     end.