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(** ** Injection from [nat] to [R]                       *)
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(** ** Injection from [Z] to [R]                         *)
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(* NOTES: - Z has 3 constructors : * Z0 : Z, representing 0 * Zpos : positive -> Z, for a positive integer * Zneg : positive -> Z, for a negative integer - Definition of Z is in Numbers.BinNums - Operations and lemmas are in ZArith (modules Z, Z2Nat, Nat2Z) *)
Lemma IZN : forall n:Z, (0 <= n)%Z -> exists m : nat, n = Z.of_nat m.