Error using "apply" function in Clojure: "Don't know how to create ISeq from: java.lang.Long"

clojure, exception, first-class-functions, higher-order-functions

Solution

The last argument to `apply` is supposed to be a sequence of arguments. In your case, the usage might look more like this:

(defn with-line-item-conditions [f price quantity] 
    {:pre [(> price 0) (> quantity 0)]
     :post [(> % 1)]} 
    (apply f [price quantity]))

`apply` is useful when you're working with a list of arguments. In your case, you can simply call the function:

(defn with-line-item-conditions [f price quantity] 
    {:pre [(> price 0) (> quantity 0)]
     :post [(> % 1)]} 
    (f price quantity))

Problem

Working on the following example in "Clojure in Action" (p. 63): ``` (defn basic-item-total [price quantity] (* price quantity)) (defn with-line-item-conditions [f price quantity] {:pre [(> price 0) (> quantity 0)] :post [(> % 1)]} (apply f price quantity)) ``` Evaluating on the REPL: ``` (with-line-item-conditions basic-item-total 20 1) ``` Results in the following exception being thrown: ``` Don't know how to create ISeq from: java.lang.Long [Thrown class java.lang.IllegalArgumentException] ``` It appears the exception is being thrown after the apply procedure is evaluated.

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