[ruby-talk:14980] Re: Array search idiom

"Dave Thomas" <[e-mail]> wrote in message
news:[e-mail]...
> "James B. Crigler" <[e-mail]> writes:
>
> > I need to find the first contiguous list of primates.  Assuming the
> > array is called "a", here's how I solved the problem.  This does
> > what I want, but is there a better way?
> ...
> > a = [
> > "insectivora. shrews", "insectivora. moles", "insectivora. hedgehogs",
> > "dermoptera. flying lemurs", "chiroptera. bats", "primates. tree
shrews",
> > "primates. lemurs", "primates. monkeys", "edentata. sloths",
> > "edentata. armadillos", "edentata. anteaters", "pholidota. scaly
anteaters",
> > "primates. marmosets", "primates. great apes", "primates. humans",
> > "lagomorpha. hares", "lagomorpha. rabbits", "lagomorpha. pikas",
> > "rodentia. mice", "rodentia. rats"
> > ]
> >
> > first_group_of_primates = Array.new
> > a.each do |line|
> >     next unless line =~ /^primates\./ .. false
> >     break if line !~ /^primates\./
> >     first_group_of_primates.push line
> > end
>
> I don't know if this is better, and it still has the extra pattern
> match on the first element of the matching subarray, but it's a
> slightly different approach.
>
>  start = len = 0
>  pat = /^primates\./
>
>  start += 1  while a[start] and a[start] !~ pat
>  len   += 1  while a[start+len] =~ pat
>
>  first_group = a[start, len]
>

Here is another try:

 pat = /^primates\./

 if start =  a.index(a.detect{|x|x =~ pat})
   last =  a.index(a[start+1..-1].detect{|x| x !~ pat})
   first_group = last ? a[start...last] : a[start..-1]
 end

>
> Regards
>
>
> Dave
>

Park Hee-Sob