til... the following works in #crystallang

[{1}, {2}, {3}].sort_by(&.first.-) # => [{3}, {2}, {1}]

because - is a method that returns the negative value of the number on which it is called. (the tuple in the example is obviously contrived...) this is in contrast to the following, which do the same thing but are more verbose:

puts [{1}, {2}, {3}].sort_by { |t| -t.first } 
puts [{1}, {2}, {3}].sort_by(&.first).reverse

one of the crystal programming language’s greatest strengths is the ease with which you can work with c apis and external libraries without leaving crystal. you can even implement callbacks in crystal!

in sqlite you can define new functions—callable from sql—with sqlite3_create_function by providing a name and a callback that implements the function. i created a new function called strip, entirely in crystal, that removes html markup and leaves text. it can be used in a sql query like so:

select * from objects
where strip(content) like "%term%"

it’s part of the recently released content filtering code.

#crystallang #ktistec