I'm writing some code using Reagent, and part of that involves writing some callbacks and state manipulation.
A few of those places will invoke functions with default arguments, and I don't want to do anything with them. I just want to return a constant value.
When I use something like #(true), for instance, I'll get an exception, and I have to write (fn [_] true). Is there a way for the lambda shorthand to know it's getting a parameter and not using it?
#(do % true)
But honestly, I just write the full version without the macro. It makes it much clearer what the intent is.
It's a shame Clojure doesn't seem to have a version of Haskell's const function. It takes a value and returns a function that throws away its argument and returns the value. Very handy for situations like this. It's trivial to write your own version for your library however:
(defn const [value]
(fn [_] value))
(some-hof (const true))
With some creativity, it probably wouldn't be difficult to make const support any number of arguments.
Edit:
@amalloy pointed out that Clojure does in fact have such a function! core/constantly.
