Saturday, September 15, 2007


pdcawley wrote the following comment to my previous "reduce" post:
[1,2,3,4].inject() {|a,b| a + b} # 10

So, I looked it up in ri and got this entry:
------------------------------------------------------ Enumerable#inject
enum.inject(initial) {| memo, obj | block } => obj
enum.inject {| memo, obj | block } => obj
Combines the elements of _enum_ by applying the block to an
accumulator value (_memo_) and each element in turn. At each step,
_memo_ is set to the value returned by the block. The first form
lets you supply an initial value for _memo_. The second form uses
the first element of the collection as a the initial value (and
skips that element while iterating).

# Sum some numbers
(5..10).inject {|sum, n| sum + n } #=> 45
# Multiply some numbers
(5..10).inject(1) {|product, n| product * n } #=> 151200
# find the longest word
longest = %w{ cat sheep bear }.inject do |memo,word|
memo.length > word.length ? memo : word
longest #=> "sheep"

# find the length of the longest word
longest = %w{ cat sheep bear }.inject(0) do |memo,word|
memo >= word.length ? memo : word.length
longest #=> 5

Ouch. All that coding for nothing (well, I did get to play around with some stuff). Next time, I will consult the documentation before I post. Duh...Good call.

P.S. It seems Rails implements the Symbol extension of #to_proc already. It's in the activesupport stuff. Their implementation is similiar to mind. But, I found one implementation better than mine. I love reading other people's code because it always shows me things I didn't think of. For your reading pleasure:

class Symbol
def to_proc
lambda do |this, *arguments|

This is better than using shift and cleaner. I got this from one of the comments off of Neal Ford's blog. Great stuff.

1 comment:

pdcawley said...

Happy to be of service.