Range weirdness

[Alex Young]

This surprised me:

C:\Documents and Settings\Alex>ruby -e "(4..1).each{|a| puts a}"

C:\Documents and Settings\Alex>ruby -e "(1..4).each{|a| puts a}"
1
2
3
4

C:\Documents and Settings\Alex>

Should it have done? I find it somewhat odd that ranges can only be
enumerated in one direction. Is there a reason for it?

 

[Tomasz Wegrzanowski]

Should it have done? I find it somewhat odd that ranges can only be
enumerated in one direction. Is there a reason for it?

There are many reason for it.

First, you need ranges with no elements.

Example:

(0 .. x.size-1).each{|i| puts x}

Now it works correctly with x=[]. It wouldn't if (0..-1) was 0.

Another example:

x = ["a", "b", "c", "d"]
p x[1..-2]

["b", "c"]

It wouldn't work either if (1..-2) meant [1,0,-1,-2].