The Moo game written in TeX

moo.tex

\def\writeln#{\immediate\write16}
\def\readln#1{{\catcode`\^^M=9 \global\read16 to#1}}

\newcount\seed \seed=1

\def\rand{\the\seed\randnext}

\def\modulo#1#2{{\count255=#1\divide\count255 by#2\multiply\count255 by#2%
  \global\advance#1by-\count255}}
\def\randnext{{%
  \global\multiply\seed by 23333
  \global\advance\seed by 12345
  \modulo\seed{32768}}}

\seed=\time

\newcount\n \newcount\i
\randnext \randnext

\def\digits{}

\i=0 \loop
  \csname newif\expandafter\endcsname\csname ifhas\the\i\endcsname
  \csname newif\expandafter\endcsname\csname ifhad\the\i\endcsname
\ifnum\i<10 \advance\i by 1 \repeat

\newif\ifagain \newif\ifhas

\i=1 \loop
  {\loop \n=\rand \modulo\n{10}
    \expandafter\let\csname ifagain\expandafter\endcsname
      \csname ifhas\the\n\endcsname
    \ifagain \repeat}
  \csname has\the\n true\endcsname
  \edef\digits{\digits\the\n}
\ifnum\i<4 \advance\i by 1 \repeat

\newcount\A \newcount\B

\def\getone#1to#2{\expandafter\dogetone\expandafter#1\expandafter#2#1\relax}
\def\dogetone#1#2#3#4\relax{\def#2{#3}\def#1{#4}}

\def\calcAB{\global\A=0 \global\B=0
  {\loop
    \ifx\digits\empty \againfalse
    \else \againtrue
      \getone\digits to\c \getone\guess to\d
      \ifx\c\d\relax\relax
        \global\advance\A by 1
      \else
        \expandafter\let\csname ifhas\expandafter\endcsname
          \csname ifhas\d\endcsname
        \ifhas \global\advance\B by 1 \fi
      \fi
    \fi
  \ifagain \repeat}}

\newif\ifvalid

\def\checkvalid{\global\validtrue{\n=0 \loop
  \ifx\guess\empty \againfalse
  \else \advance\n by 1 \againtrue
    \getone\guess to\d
    \expandafter\count255\expandafter`\d \relax
    \ifnum\count255<`0 \global\validfalse \fi
    \ifnum\count255>`9 \global\validfalse \fi
    \ifvalid
      \expandafter\let\csname ifhas\expandafter\endcsname
        \csname ifhad\d\endcsname
      \ifhas \global\validfalse \fi
      \csname had\d true\endcsname
    \fi
    \ifvalid\else \againfalse \fi
  \fi
\ifagain \repeat \ifnum\n=4\else \global\validfalse \fi}}

\loop \readln\guess
  \checkvalid
  \ifvalid
    \calcAB \writeln{\the\A A\the\B B}
  \else
    \writeln{invalid}
  \fi
\ifnum\A<4 \repeat

\bye