Hello,

First time here, and just a few hours into Racket... 
It is not going to be rocket science ;-).


Context:
 
  I am using Emacs and org-mode to map each heading of an org file to a html 
file.
  Result: one org file → one static website.
    https://github.com/phfrohring/org-to-blog

  The org file contains data that is exported to a tsv file: 
    https://github.com/phfrohring/org-to-blog/blob/master/test/blog.org#data

  A code block in the org file is evaluated:
    
https://github.com/phfrohring/org-to-blog/blob/master/test/blog.org#processing

  And produces a stacked-chart from the tsv data:
    https://github.com/phfrohring/org-to-blog/blob/master/test/blog.org#result


The tsv data is parsed into a kind of matrix `M` where each cell `M[i][j]` is a
string.  
  ex: `M[i][0]` is the column "day" i.e. contains dates
      `M[i][1]` is the column "description" i.e. contains strings

In order to use operations over "day" column (adding dates, ...) it is needed to
parse that column with something like: `iso8601->date` but not the "description"
column.

So, it is needed to apply a vector of functions `vF = [f_0,f_1,...]` to `M =
[col_0,col_1,...]` such that: `(matrix-apply vF M) = M'` where:

                M' = [f_0(col_0),f_1(col_1),...,f_n(col_n)]

Well, this function `matrix-apply` does not seem to exist and my attempt at
implementing it feels clunky to say the least (ex: fs is not a vector):

    (define (matrix-apply fs m)
      (cond [(= (length fs) (matrix-num-cols m))
             (matrix-augment
              (map (λ (f_col)
                     (apply
                      (λ (mat) (matrix-map (car f_col) mat))
                      (cdr f_col)))
                   (zip
                    fs
                    (matrix-cols m2))))]
            [#t (error fs)]))
    
    (define m2 (matrix [[1 2 3 4]
                        [1 2 3 4]]))
    
    (matrix-apply (list sqr sqr sqr sqr) m2)

    => (array #[#[1 4 9 16] #[1 4 9 16]])


Am I missing the elephant in the corridor? Is an implementation floating
somewhere? 

Thx!

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