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 OF A TERM *********************************************************)
  18
  19 let rec tw T ≝ match T with
  20 [ TSort _     ⇒ 1
  21 | TLRef _     ⇒ 1
  22 | TPair _ V T ⇒ tw V + tw T + 1
  23 ].
  24
  25 interpretation "weight (term)" 'Weight T = (tw T).
  26
  27 (* Basic properties *********************************************************)
  28
  29 axiom tw_wf_ind: ∀R:term→Prop.
  30                  (∀T2. (∀T1. #[T1] < #[T2] → R T1) → R T2) →
  31                  ∀T. R T.