Sum of rows in a matrix with lisp -

i'm doing lisp exercises using functions mapcar , apply. i'm dealing matrixes, , have sum rows , columns. column have:

(apply #'mapcar #'+ matrix) 

that works. since know how transpose matrix, can exact same thing rows right? right, be:

(apply #'mapcar #'+ (apply #'mapcar #'list matrix)) 

but i'm not happy with that. want sum row directly, did mapcar of apply:

(mapcar #'apply #'+ matrix) 

that doesn't work , don't know why. error

the value #(function +) not of type list. [condition of type type-error]

for me, every list inside matrix, , apply sum in each one. cannot make mapcar of apply? if no, why not? there way sum rows of matrix using mapcar , apply?

ps: i'm using lispstick compile , matrix list of lists. example

((1 1 1) (2 2 2) (3 3 3)) 

for 3x3 matrix.

your error

the error got mapcar expects lists arguments after 1st one, , finds function + instead.

solution

what need partial application of apply +, i.e.,

(defparameter matrix '((1 1 1) (2 2 2) (3 3 3))) (mapcar (lambda (l) (apply #'+ l)) matrix) ==> (3 6 9) 

you can define function that:

(defun partial-application (f &rest some-args)   (lambda (&rest more-args)     (apply f (append some-args more-args)))) (funcall (partial-application #'+ 4) 5) ==> 9 (funcall (partial-application #'+ 1 2) 3 4 5) ==> 15 

now can use instead of lambda:

(mapcar (partial-application #'apply #'+) matrix) ==> (3 6 9) 

notes:

1. (lambda (l) (apply #'+ l)) , (partial-application #'apply #'+) merely compute sum of list, , can defined in many different ways discussed elsewhere.

2. append cannot safely replaced non-consing verson nconc because some-args is not guaranteed fresh:

the value of rest parameter permitted, not required, share structure last argument apply.