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### Understand "curry" function

Posted: Sun Nov 25, 2018 9:28 am
This is what I understand ...

I can map a function with multiple arguments in this way:

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``````(map pow '(2 1) '(3 4))
;-> (8 1)``````
where: 8 = 2^3, 1 = 1^4
But, if the list of arguments are within a list:

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``(setq lst '((2 1) (3 4)))``
I got an error:

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``````(map pow lst)
ERR: value expected in function pow : '(2 1)``````
I use "curry" to solve this problem:

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``````(map (curry apply pow) lst)
;-> (2 81)
``````
where: 2 = 2^1, 81 = 3^4
Ok, transpose the list of arguments:

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``````(map (curry apply pow) (transpose lst))
;-> (8 1)``````
This is equivalent to:

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``````(map (lambda(x) (apply pow x)) (transpose lst))
;-> (8 1)``````
We can define a user function too:

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``````(define (mypow lst)
(if (null? lst) '()
(cons (pow (nth '(0 0) lst) (nth '(0 1) lst)) (mypow (rest lst)))
)
)``````

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``````(setq lst '((2 1) (3 4)))
(mypow (transpose lst))
;-> (8 1)``````
Another example:

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``````(map max '(3 5) '(2 7))
;-> (3 7)
(map (curry apply max) '((3 5) (2 7)))
;-> (5 7)
(map (curry apply max) (transpose '((3 5) (2 7))))
;-> (3 7)``````
Did I get it right?
cameyo
p.s. sorry for poor english...