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From: Thomas Streicher <streicher@mathematik.tu-darmstadt.de>
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Subject: Re: topos logic arising nicely
Date: Thu, 5 Jun 2003 21:46:23 +0200 (CEST)
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Hi Paul,

> "The neglect of sum types is the root of all evil."

To some extent this may be true for programming languages (but see recent
work of Jim Laird). For logics it is less clear. Actually you mean the
empty type, isn't it? Moreover, sunset types are slightly heavier than
ordinary sum types. Subset types are rather dependent sum types.

Thomas