| author | paulson |
| Wed, 13 Nov 1996 10:47:08 +0100 | |
| changeset 2183 | 8d42a7bccf0b |
| parent 2099 | c5f004bfcbab |
| child 2681 | 93ed51a91622 |
| permissions | -rw-r--r-- |
| 923 | 1 |
(* Title: HOL/Arith.thy |
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ID: $Id$ |
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Author: Lawrence C Paulson, Cambridge University Computer Laboratory |
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Copyright 1993 University of Cambridge |
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Arithmetic operators and their definitions |
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*) |
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Arith = Nat + |
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instance |
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nat :: {plus, minus, times}
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consts |
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pred :: nat => nat |
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7361ac9b024d
removed quotes from types in consts and syntax sections
clasohm
parents:
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diff
changeset
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div, mod :: [nat, nat] => nat (infixl 70) |
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defs |
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pred_def "pred(m) == case m of 0 => 0 | Suc n => n" |
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add_def "m+n == nat_rec n (%u v. Suc(v)) m" |
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diff_def "m-n == nat_rec m (%u v. pred(v)) n" |
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mult_def "m*n == nat_rec 0 (%u v. n + v) m" |
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mod_def "m mod n == wfrec (trancl pred_nat) |
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(%f j. if j<n then j else f (j-n)) m" |
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div_def "m div n == wfrec (trancl pred_nat) |
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(%f j. if j<n then 0 else Suc (f (j-n))) m" |
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end |
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(*"Difference" is subtraction of natural numbers. |
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There are no negative numbers; we have |
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m - n = 0 iff m<=n and m - n = Suc(k) iff m)n. |
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Also, nat_rec(0, %z w.z, m) is pred(m). *) |
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