Capturing Item Index in Collection - ruby

Question

I was wondering what is the proper way of finding the index of an item in an array is in a Liquid template, and selected related items based off of the index. Currently I'm able to calculate the value, but it seems to be a string and I can't then find other items in the array with the string. For example in a CMS:
{% for site_page in site.pages.all %}
{% if site_page.id == page.id %}
{% assign page_index = forloop.index0 %}
{% capture previous_page_index %}
{{ page_index | minus: 1 }}
{% endcapture %}
{% break %}
{% endif %}
{% endfor %}
The expected value can be found in previous_page_index (in this case 0) however, if i try to do something like site.pages.all[previous_page_index] I receive no output. If I do the same thing with a hardcoded index value: site.pages.all[0] it does yield an output. Does anyone have an idea/example on how this is supposed to be done in liquid?

Answer 1

Best I can figure is to use {% for item in array limit:1 offset:forloop.index0 %}. For example:
require 'liquid'
chars = %w[a b c]
names = %w[alpha bravo charlie]
puts Liquid::Template.parse(<<DONE).render( 'chars'=>chars, 'names'=>names )
{% for c in chars %}
{{c}} is
{% for n in names limit:1 offset:forloop.index0 %}{{n}}{% endfor %}
{% endfor %}
DONE
…which produces…
a is
alpha
b is
bravo
c is
charlie
Editorial aside: ouch. What an ugly tempting language. I understand its goals, but the burden it places on users is heinous.