View source for Template:Category see also/Category pair check

<includeonly>{{#ifeq: {{NAMESPACE}} | Category |<!--
 -->{{#if: {{#invoke:String|match|{{BASEPAGENAME}}|%d+[snrt][tdh]%-century.+$|ignore_errors=true}}<!--
    -->|<!-- it's on a century category
        -->{{#if: {{#invoke:String|match|{{{1|}}}|{{#invoke:String|match|{{BASEPAGENAME}}|-century.+$|ignore_errors=true}}|ignore_errors=true|plain=true}}<!--
            -->|<!-- the link is to a similar century category
                -->[[Category:Template Category see also used when Template Category pair probably should be]]<!--
        -->}}<!--
    -->}}<!--
-->}}</includeonly><noinclude>
{{doc|content=
Check whether [[Template:Category see also]] has been used when [[Template:Category pair]] probably should be use.

The test is:
#Is this page in the Category namespace?
#Does this page's title end in "nn(st|nd|rd|th))-century something"
#does the first linked cat's title end in the same "-century something" as the title of the page it is used on?

If the answer to all 3 is yes, then categorise the page in the hidden tracking category [[:Category:Template Category see also used when Template Category pair probably should be]]
}}</noinclude>