[plt-scheme] Newbie Lambda( ) (???????????)

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Fri Feb 13 14:23:12 EST 2009

Jesus, just to make sure. In case you have studied calculus,  
functions returning functions is very old. For example,

   d/dx : (Real -> Real) -> (Real -> Real)

Conventional mathematicians, though, tend to be afraid of the concept  
and therefore call these things 'operators' and 'functionals' and  
other hideous names.

Now you are ahead of these people. You have taken the first step to a  
land where all this is easy to understand, normal, and


(Think callbacks for GUIs and such stuff.)

-- Matthias

On Feb 13, 2009, at 2:13 PM, Carl Eastlund wrote:

> On Fri, Feb 13, 2009 at 1:35 PM, Jesus Boadas <jboadas at gmail.com>  
> wrote:
>> Thanks I understand now, this is new to me. My usual functions  
>> only return
>> values, never could imagine that a function could return a function
> Functions can, indeed, return functions.  In fact, functions
> themselves are values, so your function that returns a function is
> still returning a value.  It just happens to be a more interesting
> value than a number or a string.
>> I was doing some research and this is called higher order  
>> functions or I am in a
>> mistake?.
> That is correct.  Higher order functions are functions whose inputs
> and/or outputs are also functions.  They are commonplace in Scheme and
> many similar programming languages.
> --Carl
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