[mercury-users] string_stream impl, re: redirecting output to streams

[Ian MacLarty]

On 16 Feb 2006, at 03:55, Ralph Becket wrote:

> Ian MacLarty, Wednesday, 15 February 2006:
>> Not in principle, but I think you might have problems with the C code
>> that ultimately does things with the strings (for example instead of
>> passing the string to printf to write it out, you'd have to have extra
>> code to handle nulls in the string which might be an efficiency
>> problem).
>
> Many functions in the string library are O(n) rather than O(1) because
> they always do string bounds checking.  It would be better to define
>
> typedef struct { MR_Integer length; const char chars[] } MR_String;
>
> and then pass MyStr->chars to C rather than just MyStr.
>
> I think this would be a Good Change to make.
>

One question:  How do you propose to handle nulls in the writing out of 
strings?  I mean suppose I build up a string and there is a null in 
there somewhere and then I write out the string.  Should the string 
only be written out to the null, even though it's length is greater 
than the position of the null?  Certainly for binary strings you'd want 
to print the whole thing out, even the characters past the null.  This 
will require you to use something else besides printf.  Perhaps there 
should be different predicates for writing out all the characters in a 
string and for writing out only the characters up till the first null, 
but then why not have two types?

Ian.

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