utility

A swiss-army-knife of utility functions

Use with leiningen:

[erinite/utility "0.1.1"]

Reference

erinite.utility.seqs

Functions to manipulate sequences

(require '[erinite.utility.seqs :as seqs])

index-by

(fn [f col])

Transform collection col into a map of collections keyed by the result of f. Like group-by, where each key maps to the last value instead of a vector of values.

(seqs/index-by :id [{:id 1 :val "a"} {:id 2 :val "b"} {:id 3 :val "c"} {:id 1 :val "d"}])

⇒

{2 {:id 2 :val "b"}
 3 {:id 3 :val "c"}
 1 {:id 1 :val "d"}}

erinite.utility.xf

Functions to create transformation functions for use with map, update etc.

(require '[erinite.utility.xf :as xf])

when

(fn [condition xform])

Returns a transformation function that applies xform to input if applying condition is truthy, otherwise returns input unchanged.

(map (xf/when int? inc) [0 1 :foo 3 true :bar])

⇒

[1 2 :foo 4 true :bar]

cond

(fn [condition xform ...])

Returns a transformation function that applies xform to input if applying condition is truthy. Attempts each condition/xform pair in turn until condition returns truthy or no pairs remain, in which case input is returned unchanged.

(map (xf/cond int? inc keyword? name) [0 1 :foo 3 true :bar])

⇒

[1 2 "foo" 4 true "bar"]

fdefault

(fn [f v])

Returns a function which applies f only if argument is not nil, otherwise returns v.

Similar to fnil:

fnil replaces nil argument with v (and subsequent values, if provided)
fdefault replaces the call to f with v if input is nil.

(let [fnil-test (fnil inc 0)
      fdefault-test (xf/fdefault inc :default)]
  [[(fnil-test 2) (fnil-test nil)]
   [(fdefault-test 2) (fdefault-test nil)]])

⇒

[[3 1] [3 :default]]

fsome

(fn [f])

Apply f if the argument is not nil.

(map (xf/fsome inc) [0 1 nil 3 nil])

⇒

[1 2 nil 4 nil]

Erinite / utility