[r-t] Practical Extension
robin at robinw.org.uk
Sat Jul 28 10:18:01 UTC 2018
What does the Exercise know - based on previously published collections
RAS provided extensions for six-bells methods 'from the book' and
included both plain and treble dodging methods - about 15 years ago.
GACJ, MBD et al. provided extensions of all the treble-dodging Minor
methods about 18 months ago.
The fallacy, as far as I can see, is the assumption that there is always
an algorithm to find a 'contraction' - for want of a better word. This
is based upon the idea that every method and stage n is related to a
method at stage n-2. Not everything has to be an extension somehow of a
Minimus or Doubles method. Some methods have two parents.
I also have no problem with some methods being in-extensible such as
Let us take Yorkshire S8 for example. This is regarded as the progenitor
of a set of extensions. However, this is a case where, if adjacency is
removed, Yorkshire is an extension of Cambridge S6. (Someone told me on
this line once that this was nonsense, so what do I know?)
Andrew Johnson hits the obvious nail over the head. We know that there
are only eleven plain Minimus methods. The starting point is to find all
extensions of these eleven, followed by the extensions of all the
single-hunt doubles methods. This, in every day terms, is a very small
problem - there are at most 36 lead-structures with 4 lead-ends.
Finally, method extension is a practical subject and is best understood
by doing it yourself by hand. When you were at school, what did you do
in maths. lessons? You did lots and lots and lots of problems and, if
you were lucky, when you got to the exam, you didn't even have to think
much about the answer as it was almost instinctive.
You understand it by doing. You also learn from those who know how to do
it - not by assuming they don't know what they are doing!
Some years ago on this list, one or two of us were having difficulty
with the interpretation of some element by the MC of the Extension
Decision. Then one of us remarked, let us assume that the MC's
interpretation (by example) is correct, then that would enable us to
understand the Decision. As I have remarked before, having an idea is
easy, writing it down so everyone understands it immediately, or easily,
is not. It was a case of trying to find out, not how they said it, but
what they meant.
Don. Have you ever tried extending a method by hand? No? Oh, "you really
Alternatively, look at some extensions such as:
1DE/5FG &-1-23-3-3,2 (8  60)
1DE/1EF &-1-23-45-5,2 (8  60)
1DE/5EF &-1-23-23-3,2 (8  60)
4AB/2EF &-4-23-25-5,2 (8  60)
&-1-3-3,2 [St Clement's College]
1DE/5FG &-1-3-3-3,2 (8  60)
1DE/2CD &-1-1-5-5,2 (8  60)
4AB/2EF &-4-3-5-5,2 (8  60)
1DE/5FG &-1-1-5-5,1 (8  60)
1DE/4EF &-1-1-1-7,1 (8  60)
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