It turns out that I have more trouble with printing whitespace from
syntax. Consider this:
(require racket)
(require syntax/to-string)
(define (syntax-on-lines-v1 xs)
(define (iter fin ys)
(let ((y (read-syntax "<string>" fin)))
(if (eof-object? y)
(reverse ys)
(iter fin (cons y ys)))))
(if (null? xs)
'()
(let* ((fout (open-output-string))
(_ (for* ((x xs))
(writeln x fout)))
(_ (close-output-port fout))
(fin (open-input-string (get-output-string fout))))
(port-count-lines! fin)
(iter fin '()))))
The basic case works:
;; ex1
(let* ((xs '("collected" "from" "separate" "lines"))
(ys (syntax-on-lines xs)))
(syntax->string
#`(#,@ys)))
;; "\"collected\"\n\"from\"\n\"separate\"\n\"lines\""
But I need to decorate a number of constant items, such as:
;; ex2
(let* ((xs '("collected" "from" "separate" "lines"))
(ys (syntax-on-lines xs)))
(syntax->string
#`(comment #,@ys)))
;; "comment\"collected\"\"from\"\"separate\"\"lines\""
In ex2, the loss of line breaks seems to stem from lack of srcloc info
on the first token. However, I don't understand just what's necessary
to keep things moving along. If I populate the first token only with
quasisyntax/loc as follows, I get my EOLs:
;; ex3
(let* ((xs '("collected" "from" "separate" "lines"))
(ys (syntax-on-lines xs))
(zs (cons (quasisyntax/loc (car ys) "comments") ys)))
(syntax->string
#`(#,@zs)))
;; "\"comments\"\"collected\"\n\"from\"\n\"separate\"\n\"lines\""
But that's quite inconvenient if I have a bunch of stuff to decorate.
If I try to do the more convenient outside position for quasisyntax/loc,
my EOL data seems to get overwritten:
;; ex4
(let* ((xs '("collected" "from" "separate" "lines"))
(ys (syntax-on-lines xs)))
(syntax->string (quasisyntax/loc (car ys) ("comments" #,@ys))))
;; "\"comments\"\"collected\"\"from\"\"separate\"\"lines\""
Is there a way to do something like ex4, where I can add a number of new
constant tokens, but without overwriting the EOL data?
Thanks in advance,
Jeff Henrikson
On 4/9/21 9:57 AM, Jeff Henrikson wrote:
Laurent,
Thank you very much. It probably would have taken me a long time on
my own to think of the possibility that the port was at fault.
Jeff
On 4/9/21 4:29 AM, Laurent wrote:
You need to enable line/character counting with `port-count-lines!`:
#lang racket
(require syntax/to-string)
(define in (open-input-string "(comment\n \"hello world\"\n line)"))
(port-count-lines! in)
(syntax->string (read-syntax "mystring" in))
; -> "comment\n \"hello world\"\n line"
On Fri, Apr 9, 2021 at 2:10 AM Jeff Henrikson <jehenri...@gmail.com
<mailto:jehenri...@gmail.com>> wrote:
Racket users,
I’m trying to read a scheme file, decorate a bit of window
dressing around the edges, and write the expressions to a new
file. I’ve got the basic mechanism working with (read . . .) and
(pretty-write . . .), but of course that doesn’t preserve
linebreaks. So now I’m trying to improve it to preserve
linebreaks. It would be nice to preserve all whitespace, but
I'll settle for linebreaks. The racket docs seem to suggest it
is possible:
2.6 Rendering Syntax Objects with Formatting
(require syntax/to-string) package: base
procedure
(syntax->string stx-list) → string?
stx-list : (and/c syntax? stx-list?)
Builds a string with newlines and indenting according to the
source locations in stx-list; the outer pair of parens are
not rendered from stx-list.
However, when I evaluate:
(syntax->string (read-syntax "mystring" (open-input-string
"(comment\n \"hello world\"\n line)")))
I get:
"comment\"hello world\"line"
which has no whitespace at all, not even the whitespace that is
necessary to separate the original tokens.
I get a similar behavior if I read-syntax from a file and apply
syntax->string to those values.
Does anyone know how to get syntax->string to recover the
original whitespace?
I'm using Racket 8.0 cs on Ubuntu 20.
Thanks in advance,
Jeff Henrikson
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