Enumerating over an array but passing a subset of the array to the block instead of a single element

Question

I am new to ruby, and I have been reading a lot of tutorials. Yesterday I SWEAR I read an example of the each statement (or something like it) that enumerated over an array, and then passed a subset of the array to the block. Here's an example, but the syntax is wrong (or I am using the wrong method) so this will not actually run.

arry = ["a", "b", "c", "d", "e"]

arry.each(3) {|a, b, c| puts a+b+c}

If I was using the right command, this would print:abc bcd cde; it takes the first three members of the array starting at the index and the enumeration ends when there isn't a string long enough to provide all three arguments. I can't remember how to do it and I can't seem to google the right thing to find it. Do any of you guys know?

steenslag · Accepted Answer · 2012-07-05T15:01:32.637

8

each_cons(3) behaves like that. It is in Enumerable (Array includes Enumerable), that's why you couldn't find it.

edited Jul 05 '12 at 15:01

answered Jul 05 '12 at 14:56

steenslag

79,051
16
138
171

Arg!!! I read the whole Array section on ruby-doc, and then I saw that it was a child of Object so I check Object just to be sure. I totally missed that it included the Enumerables module. Thanks! – Noah Jul 05 '12 at 15:02

score 2 · Answer 2 · answered Jul 05 '12 at 14:54

2

you mean something like combination ?

arry.combination(3).each {|a, b, c| p a+b+c}

answered Jul 05 '12 at 14:54

phoet

18,688
4
46
74

This was not quite what I was looking for, but very close. Coincedentally, a problem I was working on later needed `combination` so thank you for that. :) – Noah Jul 06 '12 at 17:44

score 1 · Answer 3 · answered Jul 05 '12 at 14:55

1

How about each_slice?

arry.each_slice(3) {|a,b,c| p a+b+c}

answered Jul 05 '12 at 14:55

Linuxios

34,849
13
91
116

each slice would do a,b,c then c,d,nil not a,b,c ; b,c,d etc. as the OP wanted – Frederick Cheung Jul 05 '12 at 14:59

Enumerating over an array but passing a subset of the array to the block instead of a single element

3 Answers3