matita/matita/contribs/lambda-delta/Basic-2/grammar/term_weight.ma

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  14
  15 include "Basic-2/grammar/term.ma".
  16
  17 (* WEIGHT *******************************************************************)
  18
  19 (* the weight of a term *)
  20 let rec tw T ≝ match T with
  21 [ TSort _     ⇒ 1
  22 | TLRef _     ⇒ 1
  23 | TPair _ V T ⇒ tw V + tw T + 1
  24 ].
  25
  26 interpretation "weight (term)" 'Weight T = (tw T).
  27
  28 axiom tw_wf_ind: ∀P:term→Prop.
  29                  (∀T2. (∀T1. # T1 < # T2 → P T1) → P T2) →
  30                  ∀T. P T.