(define $integer
  (matcher
    {
     [,$n []
      {[$tgt (if (eq? tgt n)
                 {[]}
                 {})]}]
     [$ [something]
      {[$tgt {tgt}]}]
     }))

(define $compare-integer
  (lambda [$m $n]
    (if (lt? m n)
        <Less>
        (if (eq? m n)
            <Equal>
            <Greater>))))

(define $float
  (matcher
    {[,$d []
      {[$tgt (if (eq? tgt d)
                 {[]}
                 {})]}]
     [$ [something]
      {[$tgt {tgt}]}]
     }))

(define $compare-float
  (lambda [$d1 $d2]
    (if (lt? d1 d2)
        <Less>
        (if (eq? d1 d2)
            <Equal>
            <Greater>))))

(define $nat
  (matcher
    {[,$n []
      {[$tgt (if (eq? tgt n)
                 {[]}
                 {})]}]
     [<o> []
      {[0 {[]}]
       [_ {}]}]
     [<s $> nat
      {[$tgt (match (compare-integer tgt 0) ordering
               {[<greater> {(- tgt 1)}]
                [_ {}]})]}]
     [$ [something]
      {[$tgt {tgt}]}]
     }))

(define $between
  (lambda [$m $n]
    (match (compare-integer m n) ordering
      {[<less> {m @(between (+ m 1) n)}]
       [<equal> {n}]
       [<greater> {}]})))

(define $from
  (lambda [$m]
    {m @(from (+ m 1))}))

(define $min
  (lambda [$ns]
    (match ns (list integer)
      {[<cons $n <nil>> n]
       [<cons $n $rs>
        (let {[$r (min rs)]}
          (match (compare-integer n r) ordering
            {[<less> n]
             [_ r]}))]})))

(define $max
  (lambda [$ns]
    (match ns (list integer)
      {[<cons $n <nil>> n]
       [<cons $n $rs>
        (let {[$r (max rs)]}
          (match (compare-integer n r) ordering
            {[<greater> n]
             [_ r]}))]})))

(define $min-and-max
  (lambda [$ns]
    (match ns (list integer)
      {[<cons $n <nil>> [n n]]
       [<cons $n $rs>
        (let {[[$min-n $max-n] (min-and-max rs)]}
          (match (compare-integer n min-n) ordering
            {[<less> [n max-n]]
             [_ (match (compare-integer n max-n) ordering
                  {[<greater> [min-n n]]
                   [_ [min-n max-n]]})]}))]})))

(define $gcd
  (lambda [$ns]
    (match ns (set integer)
      {[<cons $n <nil>> n]
       [<cons (& ,(min ns) $m)
              $rs>
        (gcd {m @((remove-all integer)
                                       (map (lambda [$r] (mod r m))
                                            rs)
                                       0)})]})))

(define $fib
  (lambda [$n]
    (letrec {[$fib1 (lambda [$n $ret1 $ret2]
                      (match n nat
                        {[<o> ret2]
                         [<s <o>> ret1]
                         [<s $n1> (fib1 (- n 1) (+ ret1 ret2) ret1)]
                         }))]}
      (fib1 n 1 1))))


(define $fact
  (lambda [$n]
    (letrec {[$fact1 (lambda [$n $ret]
                       (match n [nat]
                         {[<o> ret]
                          [<s $n1> (fact1 n1 (* n ret))]}))]}
      (fact1 n 1))))

(define $mod
  (lambda [$m]
    (matcher
      {[,$n []
        {[$tgt (if (eq? (modulo tgt m) (modulo n m))
                   {[]}
                   {})]}]
       [$ [something]
        {[$tgt {(modulo tgt m)}]}]
       })))