cast — Mathlib

English

If s ∈ X.N has dimension d, then s.cast hd is the same element but viewed as dimension d.

Русский

Если s ∈ X.N имеет размерность d, то s.cast hd то же самое значение, но с размерностью d.

LaTeX

$$$\text{cast} : X.N \to X.N$ (given hd) is identity on the element with matching dimension.$$

Lean4

/-- When `s : X.N` is such that `s.dim = d`, this is a term
that is equal to `s`, but whose dimension if definitionally equal to `d`. -/
abbrev cast : X.N where
  toS := s.toS.cast hd
  nonDegenerate := by
    subst hd
    exact s.nonDegenerate

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