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From: saharbaugh%roo.dnet@WINNIE.BERKELEY.EDU
Newsgroups: comp.lang.ada
Subject: "BIG E vs little e", was pre-condition vs post-condition
Message-ID: <9103161431.AA07643@winnie.fit.edu>
Date: 16 Mar 91 14:31:31 GMT
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Re: The discussion titled: "Pre-Condition vs Post-Condition"

Mike Feldman invites further discussion so here is a "war story":

In 1982 we were defining the Ada/GKS binding.  The ANSI GKS spec  
specified that an error code be returned to the caller (ala Fortran).  
Our challenge was to determine which error codes would be 
implemented in Ada as error codes and which error codes would be 
implemented as Ada exceptions.

I defined a partitioning criteria I called "BIG E vs little e".  A "little e" 
would be a soft error such as the caller asking for a red polyline on a 
monochrome workstation.  A "BIG E" would be hard error such as the 
caller asking for a red polyline on a workstation which is off-line.

Little e's allow the programmer to continue the train of thought 
through the graphics program.  BIG E's force the programmer the 
break the train of thought and deal with an unexpected situation.


sam harbaugh  saharbaugh%ROO.DNET@WINNIE.FIT.EDU       
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