24 lines
686 B
Text
24 lines
686 B
Text
namespace experiment
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inductive nat : Type
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| zero : nat
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| succ : nat → nat
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namespace nat
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definition plus (x y : nat) : nat
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:= nat.rec x (λn r, succ r) y
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definition to_nat (n : num) : nat
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:= num.rec zero (λn, pos_num.rec (succ zero) (λn r, plus r (plus r (succ zero))) (λn r, plus r r) n) n
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definition add (x y : nat) : nat
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:= plus x y
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constant le : nat → nat → Prop
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infixl `+` := add
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infix `≤` := le
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axiom add_one (n:nat) : n + (succ zero) = succ n
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axiom add_le_right {n m : nat} (H : n ≤ m) (k : nat) : n + k ≤ m + k
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theorem succ_le {n m : nat} (H : n ≤ m) : succ n ≤ succ m
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:= add_one m ▸ add_one n ▸ add_le_right H (to_nat (1:num))
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end nat
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end experiment
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