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Re: [Bug-mit-scheme] A killer -- system just disappears!

From: Taylor R Campbell
Subject: Re: [Bug-mit-scheme] A killer -- system just disappears!
Date: Fri, 18 Feb 2011 03:34:50 +0000
User-agent: IMAIL/1.21; Edwin/3.116; MIT-Scheme/9.0.1 
   Date: Thu, 17 Feb 2011 22:21:53 -0500
   From: Gerald Jay Sussman <address@hidden>

   Try ((entity-extra #f) 'foo).
   ;Hardware trap SIGSEGV: "address not mapped to object"

ENTITY-EXTRA and SET-ENTITY-EXTRA! don't check their argument types.
I guess you're not supposed to use them unless you've checked
yourself...  Maybe once upon a time there was a performance reason for
this?

We really need a more principled type checking system like Racket's
contracts.  The GUARANTEE-* procedures are a little silly and rather
clumsy.
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