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Reading symbols commutes with taking prefix of tapes

Proved
read_take

by junyihjy · Sep 22, 2026 · Mathlib 0df444a (Lean v4.33.1)

Reading the symbols under the heads of the first k1 tapes equals taking the first k1 symbols from reading all tapes.

Formal statement
import Definitions.Def_CookLevin_Basic

open CookLevin

theorem read_take (tps : List Tape) (k1 : Nat) :
    read (tps.take k1) = (read tps).take k1 := by sorry

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