[MLton] getting String.fromString to return NONE
Michael Norrish
Michael Norrish <Michael.Norrish@nicta.com.au>
Mon, 31 Jul 2006 10:48:19 +1000
Stephen Weeks writes:
> Short answer: don't use String.fromString.
Thanks for this (I appreciate the extra detail of the long answer). I
ended up writing my function from scratch.
I wanted to emulate the SML lexing rules for HOL's own type of
strings. Moscow ML's behaviour of accepting "\n" and "\t" (and others
no doubt) meant that I couldn't use Moscow ML's fromString. Further,
having fromString return the prefix is not a great deal of use either.
I hadn't appreciated that there was a scan function (the fault lies
with Moscow ML implementing just the old Basis), which would at least
have given me the suffix too.
But I totally agree that your intuition is the right one. You'd think
that the Basis Library would make writing an SML lexer/parser easy.
It also seems to be a great case study in the ambiguity of prose
specifications.
Michael.