Author: Tony Werten
Date: 01:30:58 08/11/02
Go up one level in this thread
On August 10, 2002 at 16:37:46, Alessandro Damiani wrote: >On August 10, 2002 at 07:06:55, Tony Werten wrote: > >>On August 10, 2002 at 05:59:08, Alessandro Damiani wrote: >> >>>On August 10, 2002 at 03:43:49, Tony Werten wrote: >>> >>>>On August 10, 2002 at 03:06:36, Ed Schröder wrote: >>>> >>>>>On August 09, 2002 at 18:52:56, GuyHaworth wrote: >>>>> >>>>>> >>>>>>Yes, a sad loss. A remarkable man. >>>>>> >>>>>>"GOTO considered harmful" and "Co-operating Sequential Processes" had a major >>>>>>effect on my thinking in the '70s. >>>>> >>>>>Together with Jackson he was one of the pioneers of "Modular Programming", in >>>>>the late 70's I had to learn his stuff. The one thing he could not convince me >>>>>is the use of the "goto" instruction, I still use it. The use of the "goto" >>>>>instruction is considered as the no.1 main sin in programming. >>>> >>>>Not anymore I think. Break and continue are considered correct instructions >>>>while basicly they are a goto. >>>> >>> >>>What is the postcondition of a "break"? ;) >> >> >>repeat >> >> some code; >> >> // break or continue >> >> more code; >> >>until (x>5); // continue will make you jump here, so skip more code is skipped >> >> >>// break will make you jump here >> >>Tony >> > >I know "break" and "continue". The problem with them is that their postcondition >does not depend on the statement itself, since it is just a jump. If we look at >a Hoare triplet for the break-statement we cannot determine the postcondition >for "break". Yes, you seem to be right. The problem seems to be that break and continue are regarded as exceptions wich is quite silly. Break is just a goto, continue can be seen as a goto or as a big if clause including everything up to the until statement. Tony > >Alessandro
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