Documentation

Mathlib.Algebra.Group.Fin.Basic

Fin is a group #

This file contains the additive and multiplicative monoid instances on Fin n.

See note [foundational algebra order theory].

Instances #

Equations
    instance Fin.addCommMonoid (n : ) [NeZero n] :
    Equations
      instance Fin.addCommGroup (n : ) [NeZero n] :
      Equations

        Note this is more general than Fin.addCommGroup as it applies (vacuously) to Fin 0 too.

        Equations

          Note this is more general than Fin.addCommGroup as it applies (vacuously) to Fin 0 too.

          Note this is more general than Fin.addCommGroup as it applies (vacuously) to Fin 0 too.

          Equations

            Note this is more general than Fin.addCommGroup as it applies (vacuously) to Fin 0 too.

            Equations

              Miscellaneous lemmas #

              theorem Fin.coe_sub_one {n : } (a : Fin (n + 1)) :
              ↑(a - 1) = if a = 0 then n else a - 1
              @[simp]
              theorem Fin.lt_sub_iff {n : } {a b : Fin n} :
              a < a - b a < b
              @[simp]
              theorem Fin.sub_le_iff {n : } {a b : Fin n} :
              a - b a b a
              @[simp]
              theorem Fin.lt_one_iff {n : } (x : Fin (n + 2)) :
              x < 1 x = 0
              theorem Fin.lt_sub_one_iff {n : } {k : Fin (n + 2)} :
              k < k - 1 k = 0
              @[simp]
              theorem Fin.le_sub_one_iff {n : } {k : Fin (n + 1)} :
              k k - 1 k = 0
              theorem Fin.sub_one_lt_iff {n : } {k : Fin (n + 1)} :
              k - 1 < k 0 < k
              @[simp]
              theorem Fin.neg_last (n : ) :
              -last n = 1
              theorem Fin.neg_natCast_eq_one (n : ) :
              -n = 1
              theorem Fin.rev_add {n : } (a b : Fin n) :
              (a + b).rev = a.rev - b
              theorem Fin.rev_sub {n : } (a b : Fin n) :
              (a - b).rev = a.rev + b
              theorem Fin.add_lt_left_iff {n : } {a b : Fin n} :
              a + b < a b.rev < a