So a kind of pretty-printing for at-expressions?
I'm not aware of an existing procedure to do this.
It has some interesting wrinkles. Following is my "Greenspun's Tenth
Rule" version. (An ad hoc, informally-specified, bug-ridden, slow
implementation of half of what's probably needed.)
I've commented some deficiencies, I suspect there are many more.
#lang racket
;; IMPROVE-ME: Make something usable as a pretty-print-handler
(define (print/at-exp stx-or-sepxr)
(match stx-or-sepxr
[(? syntax? stx) (print/at-exp (syntax->datum stx))]
[(list (? symbol? f)
(? (negate string?) xs) ...
(? string? ss) ...
ys ...)
(display #\@)
(display f)
(unless (empty? xs)
(display #\[) (display (string-join (map ~a xs) " ")) (display #\]))
(unless (and (empty? ss) (empty? ys))
(display #\{)
(for ([v (in-list (append ss ys))])
(cond [(string? v) (display v)]
;; FIXME: Encode @ as @"@"
;; IMPROVE-ME: Surround in pipe chars only when necessary
;; IMPROVE-ME: Do line-wrapping at column N.
[else (display "@|")
(display v)
(display "|")]))
(display #\}))]
[(list (? symbol? f) vs ...)
(display #\@)
(display f)
(display #\[) (display (string-join (map ~v vs) " ")) (display #\])]
[v (print v)]))
(print/at-exp #'(foo 1 2)) (newline)
(print/at-exp #'(foo 1 2 "a")) (newline)
(print/at-exp #'(foo 1 2 "a b")) (newline)
(print/at-exp #'(foo 1 2 "a b")) (newline)
(print/at-exp #'(foo "a")) (newline)
(print/at-exp #'(foo "a" "b")) (newline)
(print/at-exp #'(foo "a " "b")) (newline)
(print/at-exp #'(foo "a is " a " and b is " b)) (newline)
(print/at-exp #'(foo "a" "b" 1 2)) (newline)
(print/at-exp #'(foo "The " (code "x") " argument.")) (newline)
Output:
@foo[1 2]
@foo[1 2]{a}
@foo[1 2]{a b}
@foo[1 2]{a b}
@foo{a}
@foo{ab}
@foo{a b}
@foo{a is @|a| and b is @|b|}
@foo{ab@|1|@|2|}
@foo{The @|(code x)| argument.}
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