Re: Questions about floating numbers, rethink and bug report

[Per Bothner]

Chris Cramer wrote:

> R5RS compliance is great, but I really think that is going too far. If
> you do it that way, there's a way to specify read-only literals, but
> there's no way to specify writable literals,
There is no such thing as a "writable literal", since a literal refers 
to the
program text.  There are objects whose value is specified by a literal, or
(if you prefer) literals that are read as writable objects.  However, 
writing
to an object that was read from a literal is like replacing the literal 
"5.0".
While some old Fortran compilers would let you to that, no-one claimed
that as a feature.  It is just made for hard-to-catch bugs.

> For instance, in C, you can do
>
>         const static char foo[] = "blah";
>
> which will make it read-only, or you can do
>
>         static char foo[] = "blah";
In Scheme you can do:
   "blah"  ;; constant
or:
   (string #\b #\l #\a #\h) ;; writable
or:
 (copy-string "blah") ;; writable

Similarly, for vectors:
 #(3 4 5)  ;; constant
vs:
 (vector 3 4 5) ;; writable