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varfn



    macro
    boot.janet on line 2042, column 1

    (varfn name & body)

    Create a function that can be rebound. varfn has the same signature 
    as defn, but defines functions in the environment as vars. If a var 
    'name' already exists in the environment, it is rebound to the new 
    function. Returns a function.

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(var a nil)

(var b nil)

(varfn a
  [x]
  (if (zero? x)
    0
    (b x)))
    
(varfn b
  [y]
  (if (pos? y)
    1
    (a y)))
    
(a 1)
# => 1

(b 0)
# => 0

sogaiuPlayground

(defn greet-me [] (print "hey programmer!"))
(defn greet-stranger [] (print "hey stranger!"))

(varfn greet [] (greet-me))
(greet) # prints "hey programmer!"
(varfn greet [] (greet-stranger))
(greet) # prints "hey stranger!"

# kind of analogous to (def greet (fn [] (some-thunk))), but with built-in
# sugar to automatically update 'greet' if varfn is called with a name
# already bound

wrqPlayground