Re: PIZZA time again :-)
From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Fri, 02 Sep 2005 22:21:56 +0200
Message-ID: <4318b45c$0$11069$e4fe514c_at_news.xs4all.nl>
>>dawn wrote:
>>>mAsterdam wrote:
>>>
>>>>>>Assume
>>>>>>1. there is a meaningful (or at least consequential)
>>>>>>difference between:
>>>>>>
>>>>>> toppings([salami, mozarella, onions]).
>>>>>> and
>>>>>> toppings([mozarella, onions, salami]).
>>
>>[snip]
>>
>>>>Consider
>>>>
>>>> merge(ListOfLists, MergedList).
>>>>
>>>>Now
>>>>
>>>>merge ([[salami, mozarella, onions][mozarella, onions, salami]], M).
>>>>
>>>>should fail because salami is before mozarella in the first list,
>>>>and after it in the second. It can't preserve the order.
>>>
>>>I don't know how you define a merge when there isn't
>>>an ordering defined on the type.
>>>Is there such a function? Your lists are ordered here,
>>>but your domain/type is not, unless you choose something
>>>like alpha order.
>>
>>That is another way of asking the same question.
>>What should 'merge' do when the order is not
>>in the values (as it would be if we took the
>>ordering defined on the type) but just in
>>their position, relative to other values.
>>It is what I'm trying to find out.
Date: Fri, 02 Sep 2005 22:21:56 +0200
Message-ID: <4318b45c$0$11069$e4fe514c_at_news.xs4all.nl>
vc wrote:
> mAsterdam wrote:
>>dawn wrote:
>>>mAsterdam wrote:
>>>
>>>>>>Assume
>>>>>>1. there is a meaningful (or at least consequential)
>>>>>>difference between:
>>>>>>
>>>>>> toppings([salami, mozarella, onions]).
>>>>>> and
>>>>>> toppings([mozarella, onions, salami]).
>>
>>[snip]
>>
>>>>Consider
>>>>
>>>> merge(ListOfLists, MergedList).
>>>>
>>>>Now
>>>>
>>>>merge ([[salami, mozarella, onions][mozarella, onions, salami]], M).
>>>>
>>>>should fail because salami is before mozarella in the first list,
>>>>and after it in the second. It can't preserve the order.
>>>
>>>I don't know how you define a merge when there isn't
>>>an ordering defined on the type.
>>>Is there such a function? Your lists are ordered here,
>>>but your domain/type is not, unless you choose something
>>>like alpha order.
>>
>>That is another way of asking the same question.
>>What should 'merge' do when the order is not
>>in the values (as it would be if we took the
>>ordering defined on the type) but just in
>>their position, relative to other values.
>>It is what I'm trying to find out.
> > Since 'merge' is commonly defined for lists with the same ordering, the > function cannot be applied to lists with different orderings, e.g [a, > b] and [b,a,c] (ordering is defined by an element position in the list) > clearly cannot be merged.
That is the merge as used in some sorting algorithms, not a merge in it's own right. But if you feel more comfortable calling the discussed merge mymerge, truemerge, falsemerge or order_preserving_merge - ok. Received on Fri Sep 02 2005 - 22:21:56 CEST