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# First class functions

* an essential feature of functional language
* Functions are described as first-class when they can be treated like any other value: that is to say,
  * they can be dynamically assigned to a name or symbol at runtime
  * they can be stored in data structures
  * passed in via function arguments
  * returned as function return values
* Similar to how pointers work
* Also called Lambdas
  * lambdas are unnamed/annoymous functions
  * The point of a lambda function is where you need a function in that place and only there; since it is not needed anywhere else you simply define it right there. It doesn’t need a name.
    * If you did need to reuse it somewhere else then you would consider defining it as a named function and referencing it by name instead
* As function/lambda is passed as a variable (or is function form)
  * it is not called immediately
  * it can be called/invoked by whoever it was passed to
* First-class functions are also the means for achieving asynchronous I/O
  * allows to make non-blocking function call
  * you pass it a reference to a function for it to call you back on when it is done


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