Is there a way to format keys/values like raise-arguments-error

[David Storrs]

raise-arguments-errors produces neatly stacked key/value pairs with whitespace arranged such that values line up even when keys are of different lengths.  Is there an easy way to get that for something that is not an error?  I've been through both The Printer and the raise-arguments-error sections in the Reference and can't find anything.

For example:

(doit "x" 1 "foo" 2 "super" 3)

Returns the string "x     1\nfoo   2\super 3"

[kamist...@gmail.com]

I am not really aware of a function that does this you could try digging into the implementation of raise-arguments-error,

usually I roll my own implementation depending on what I really want to output.

racket/format and its ~a, ~v, etc. have a lot of useful optional keyword arguments like #:align #:pad-string #:width etc.

This isn't totally what you want, but maybe it has something that is useful to you.

This or similar code is what I have used sometimes:

#lang racket

(define current-prefix-length (make-parameter 0))
(define (prefixln #:prefix [prefix ""]
                  #:align  [align 'left]
                  . message)
  (displayln (apply ~a (list* (~a prefix #:width (current-prefix-length) #:align align)
                              message))))

(define-syntax-rule (with-indent body ...)
  (parameterize ([current-prefix-length (+ (current-prefix-length) 2)])
    body ...))

(define (example-func1)
  (prefixln "start of example func1")
  (with-indent
    (example-func2))
  (prefixln "end of example func1"))

(define (example-func2)
  (prefixln "start of example func2")
  (prefixln "end of example func2"))


(module+ main

  (displayln "Hello checkout these values:")
  (define example-values
    (hash 'foo 123
          'this-is-a-long-key "some value"
          'blabla #f
          "cake" "is a lie"))

  ;; ugly oneliner to calculate prefix width
  (current-prefix-length (+ 2 (foldl max 0 (map (compose1 string-length ~a) (hash-keys example-values)))))

  (for ([(k v) (in-hash example-values)]) ;; probably sorting or assoc list would make sense too...
    (prefixln #:prefix (~a k ": ") #:align 'right
              v))

  (current-prefix-length 0)
  (displayln "")
  (displayln "indentation through multiple nested calls:")
  (with-indent
    (example-func1)))

If you use a current-prefix-string parameter instead you can create other interesting things like lines indented with indentation level indicators, etc.:
indent0
| indent1

| | indent2

| indent1

indent0

But I am getting too off-topic...

Simon

[Laurent]

Maybe take a look at the text-table package.

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[David Storrs]

Wow, thank you Simon.  That was above and beyond.

I should have thought of ~a to start with.  With your pointers I came up with a less flexible solution that is sufficient to the current issue:

#lang racket/base

(require racket/format

         racket/string)

(define my-keys   '("bacon" "eggs" "pancakes"))
(define my-vals   '("turkey" "whites" "blueberry"))

(define (make-str keys vals)
  (define width (apply max (map string-length keys)))
  (string-join
   (for/list ([k keys]
              [v vals])
     (format "\t~a" (~a (~a k #:width width) v #:separator "\t")))
   "\n"))

(displayln (make-str my-keys my-vals))

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[David Storrs]

Thank you, Laurent.  That's a cool package; I think it would work well to generate tables suitable for org-mode spreadsheets.  I could even pull data from a sqlite DB, giving me power and portability without needing an internet connection or a full heavyweight spreadsheet app.

[kamist...@gmail.com]

I like the apply max instead of foldl, quite a bit easier.

Instead of `(format "\t~a" (~a (~a k #:width width) v #:separator "\t"))` I prefer one of these:

(~a "\t" (~a k #:width width) "\t" v)

(~a #:separator "\t" "" (~a k #:width width) v)

[David Storrs]

Fiiiiine.  If you want to be all efficient and readable, go right ahead.

Thanks, applied.  :>

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