function
boot.janet on line 1126 , column 1
(count pred ind & inds )
Count the number of values in a data structure `ind` for which
applying `pred` yields a truthy value , but only if no `inds` are
provided. Multiple data structures can be handled if each `inds` is
a data structure and `pred` is a function of arity one more than
the number of `inds` . Note that `pred` is only applied to values at
indeces up to the largest index of the shortest of `ind` and each
of `inds` .
(count even? [1 2 3 4 5 ]) # => 2
(count (fn [x ] ( x 3 )) [1 2 3 4 5 ]) # => 2
(count |( $ 3 ) [1 2 3 4 5 ]) # => 2
(count (fn [x ] (truthy? x )) [nil false true 42 :a "foo" ]) # => 4
(count |(truthy? $ ) [nil false true 42 :a "foo" ]) # => 4
(var f even? )
(count f [1 2 3 4 5 ]) # => 2
(set f odd? )
(count f [1 2 3 4 5 ]) # => 3
(map (fn [f ] (count f [1 2 3 4 5 ])) [even? odd? ]) # => @[2 3]
(map |(count $ [1 2 3 4 5 ]) [even? odd? ]) # => @[2 3]