Saturday, November 24, 2007
How I've been spending my time off work lately
The weather being fine, and in the flagrant pursuit of happiness, I’ve managed to get a few holes in this week (using Ruby of course). Here’s my scorecard:
Perhaps Guido has a point, indentation matters:
Hmmm. Still doesn’t make any sense. I guess home-brew programs are like babies: they appear to be delightful and impart a sense of wonder in the mysteries of the universe to their creators, but are noisy and obstreperous to everyone else.
palindrome = (+(+[] | +[-:_] | ((-'[0]' >> -:ends) & (-'[1..-2]' >> -:p)
& (-'[-1]' >> -:ends) & -:_)) >> (-:'{}' >> -:p)).call
(palindrome =~ []).should_not be_nil
(palindrome =~ [:fish]).should_not be_nil
(palindrome =~ [:fish, :dog]).should be_nil
(palindrome =~ [:fish, :dog, :fish]).should_not be_nil
(palindrome =~ [:fish, :fish, :fish, :fish]).should_not be_nil
(palindrome =~ [:fish, :fish, :fish, :fish, :fish]).should_not be_nil
(palindrome =~ [:fish, :dog, :dog, :fish]).should_not be_nil
(palindrome =~ [:fish, :dog, :cat, :dog, :fish]).should_not be_nil
(palindrome =~ [:fish, :dog, :cat, :fish]).should be_nilPerhaps Guido has a point, indentation matters:
palindrome = (
+( # we'll start by creating a pattern
+[] | # match the empty list, or:
+[-:_] | # match a list containing anything
# (-:_ matches any one entity), or:
( # alternative three:
(-'[0]' >> -:ends) & # extract the first element and
# bind it to 'ends'
(-'[1..-2]' >> -:p) & # and everything from the second to the
# second-last will be matched against a
# pattern :p
(-'[-1]' >> -:ends) & # and the last element must match whatever
# was bound to 'ends' above.
# it's equally effective to include
# -'_[0].eql?(_[1])', same thing.
-:_ # if all that matches, match the entire array
# so that the result is the entire array, not
# whatever part of the array we were just
# matching
) # therein ends the pattern
) >> (-:'{}' >> -:p) # pass the pattern to a closure-maker (-:'{}')
# and then bind it to 'p' so that the pattern
# is now recursive: this pattern matches an
# empty list, a list with one element, or
# a list with the first and last elements eql?
# to each other and whatever is in-between them
# matching the palindrome pattern bound to 'p'.
).callHmmm. Still doesn’t make any sense. I guess home-brew programs are like babies: they appear to be delightful and impart a sense of wonder in the mysteries of the universe to their creators, but are noisy and obstreperous to everyone else.
f = (
+(
(-'==0' >> -'0') |
(-'==1' >> -'1') |
(-'n>1' >> -'n * f[n-1]') ) >> (-:'{}' >> -:f)).call
f[0].should == 0
f[1].should == 1
f[2].should == 2
f[3].should == 6
f[4].should == 24
f[5].should == 120Labels: ruby
Thank you for reading my work. Did you enjoy this post? You can find more like it in the sidebar. Please browse the archives, there are lots of hidden gems. A Brief History of Dangerous Ideas explains what I am up to at the moment.
Hm. I get the following when I try it:
SyntaxError: compile error
(irb):2: syntax error, unexpected tAMPER, expecting ')'
& (-'[-1]' >> -:ends) & -:_)) >> (-:'{}' >> -:p)).call
^
Are you forgetting to tell us something? :)
SyntaxError: compile error
(irb):2: syntax error, unexpected tAMPER, expecting ')'
& (-'[-1]' >> -:ends) & -:_)) >> (-:'{}' >> -:p)).call
^
Are you forgetting to tell us something? :)
Matt, now you know why I am not big on using "FizBuzz" interviews. I would probably mix up the fizzing and buzzing!
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