Re: i am a prolog beginner pls help me in getting this

jaya chandra wrote:
On Apr 18, 11:22 pm, jaya chandra <rams.13...@xxxxxxxxx> wrote:
On Apr 18, 1:26 pm, Jussi Piitulainen <jpiit...@xxxxxxxxxxxxxxxx>
wrote:



jaya chandra writes:
Joachim Schimpf wrote:
rams.13...@xxxxxxxxx wrote:
?- everyother([3,4,11,0,9,19],X).
X = [3, 11, 9] ;
No
[snip]
This code gives the answers you want:
everyother([3,4,11,0,9,19],[3, 11, 9]).
...
hey thanku for the help.but it should be written generally means not
only for that numbers but for all the input please help me in the
code pls help
Can you write a solution for lists of length one? Lists of length two?
Lists of length at most two? List of length at most three?
we have to write a program which gives output for the following
examples


I am asking [for a definition of the] 'everyother' function, man.


Has it occurred to you that you might be able to derive the
sought-after general definition on your own?

You should always begin by writing down an ordinary definition of the
Prolog predicate you want.

E,g,

eo(L1,L2) is true if and only if list L2 consists of
the odd-numbered members of list L1 in the order they occur.

Examples:

eo([a],[a]).

eo([a,b],[a]).

eo([a,b,c],[a,c]).

The examples generalize easily:

eo([X1],[X1]).
eo([X1,X2],[X1]).
eo([X1,X2,X3],[X1,X3]).

This leaves the case of lists with or more members.

eo([X1,X2,X3,X4|L1],[X1,X3|L2]) if something...

Furthermore, the empty list contains no members, hence no odd-numbered
members, so we /must/ admit

eo([],[]).

Collecting the bits and piece of our fragmentary provisional
definition, and some tidying up, we get

eo([],[]).
eo([X1],[X1]).
eo([X1,_],[X1]).
eo([X1,_,X3],[X1,X3]).
eo([X1,_,X3,_|L1],[X1,X3|L2]) :- something... .

which, after you supply the missing "something", can be tested in
the Prolog Inference Engine and further simplified.

Prolog resembles a piano more that it resembles a hammer: any moron
can hit himself on the head with a hammer the first the he sees one, but
no-one can sit down and start playing Rachmaninov the first time he
sees a piano.

Practice, man, practice! :)

billh

.

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