hott/List+.thy


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theory "List+"
imports
  Spartan.List
  Nat

begin

section \<open>Length\<close>

definition [implicit]: "len \<equiv> ListRec ? Nat 0 (fn _ _ rec. suc rec)"

experiment begin
  Lemma "len [] \<equiv> ?n" by (subst comp)
  Lemma "len [0, suc 0, suc (suc 0)] \<equiv> ?n" by (subst comp)
end


end