author  clasohm 
Tue, 30 Jan 1996 13:42:57 +0100  
changeset 1461  6bcb44e4d6e5 
parent 1450  19a256c8086d 
child 9907  473a6604da94 
permissions  rwrr 
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(* Title: ZF/Let 
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ID: $Id$ 
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Author: Lawrence C Paulson, Cambridge University Computer Laboratory 
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Copyright 1995 University of Cambridge 
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Let expressions  borrowed from HOL 

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*) 

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open Let; 

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val [prem] = goalw thy 

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[Let_def] "(!!x. x=t ==> P(u(x))) ==> P(let x=t in u(x))"; 

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by (rtac (refl RS prem) 1); 
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qed "LetI"; 