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Re: explicit quoting/unquoting of strings

This page is part of the web mail archives of SRFI 75 from before July 7th, 2015. The new archives for SRFI 75 contain all messages, not just those from before July 7th, 2015.

If Scheme had a standard notion of string ports, then except for the
state part, these conversions could be implemented easily with string
ports, `write', and `read'. (For the state part of `string-unquote',
it seems like you really want a stream and `read', anyway.)

My personal opinion --- which, as always, not an opinion from the
editors --- is that string ports should be added to Scheme, and
functions like this should be left to another library.


At Tue, 12 Jul 2005 11:58:18 +0200, Sebastian Egner wrote:
> The SRFI specifies an escape mechanism for expressing strings in a
> reduced character set (Section "Quoted strings").
> It would substantially increase portability and convenience if the quoting
> and unquoting mechanism is also made available explicitly to application
> programs---for example through procedures like this:
> (string-quote str)
>         produces a representation of string str in the reduced set of 
> characters
>         <<specify here>> by introducing backslash escape sequences.
>         The result is a newly allocated string s satisfying
>                 (string=? (string-unquote s) str)
> (string-unquote str [ state ] ) -> str' state'
>         interprets backslash escape sequences in string str and constructs 
> the
>         string being represented.
>             The optional argument state, and the second return value 
> state',
>         represent the state of the interpreter (a finite state machine) 
> before and
>         after processing str. By passing the state from one invokation of
>         string-unquote to the next, it is possible to unquote arbitrary 
> substrings
>         of a stream of characters---even if the stream is broken within 
> escape
>         sequences. The state #f (default for state) is the start state 
> (taking letters
>         etc. at face value.) Other states are <<specify?; need to know?; 
> ints?>>.
> ----
> Dr. Sebastian Egner
> Senior Scientist
> Philips Research Laboratories
> Prof. Holstlaan 4 (WDC 1-051, 1st floor, room 51)
> 5656 AA Eindhoven
> The Netherlands
> tel:       +31 40 27-43166
> fax:      +31 40 27-44004
> email: sebastian.egner@xxxxxxxxxxx