looping over jekyll collections - loops

Question

I have the following code
<div>
{% for note in site.regnotes %}
{% if note.regulationno == page.regulationno %}
<p>
{{ note.regulationno }} - {{ note.url }}
</p>
{% endif %}
{% endfor %}
</div>
This code loops over the regnotes collection in a jekyll site, checks if the current note regulationno is the same as the page regulationno and if so displays the regulationno and url - that is the url of the current page. How do I change this code to include the url of the previous page, the current page and the next page. I'm looking for three urls - previous, current and next? - The "page.previous.url" variable within jekyll does not appear to work in collections.
This is what it might look like in other code
for i=1 to number of items in the regnotes collection
if current note == page note
print page[i].url //current page url
print page[i-1].url //previous page url
print page[i+1].url //next page url
end if
end for
I suppose what I'm trying todo is reference the items in the collection by their array index. just can't seem to get the syntax correct.

Answer 1

Since you are a programmer, you just need to know that you need to use forloop.index0 to know where you are in the for loop (https://docs.shopify.com/themes/liquid-documentation/objects/for-loops#index0).
The code will be something like:
<div>
{% for note in site.regnotes %}
{% assign current_index = forloop.index0 }}
{% assign next_index = current_index | plus: 1 %}
{% assign prev_index = current_index | minus: 1 %}
{% if note.regulationno == page.regulationno %}
<p>
{{ note.regulationno }} - {{ note.url }}
</p>
{% if site.regnotes[prev_index] %}prev{% endif %}
{% if site.regnotes[next_index] %}next{% endif %}
{% endif %}
{% endfor %}
</div>