Re: 1980 Basic Sought

<ArarghMail804NOSPAM@[EMAIL PROTECTED]
> wrote in message 
news:vjfmv318ej8a3ls16s4ovc2qgnpvgs6gdv@[EMAIL PROTECTED]
> On Tue, 8 Apr 2008 04:35:55 -0400, "Tom Lake" <tlake@[EMAIL PROTECTED]
>
> wrote:
>
>>
>>
>><ArarghMail804NOSPAM@[EMAIL PROTECTED]
> wrote in message
>>news:ftvlv35geav069m24gptsieot401nno8uq@[EMAIL PROTECTED]
>>> On Mon, 7 Apr 2008 23:08:17 -0400, "Tom Lake" <tlake@[EMAIL PROTECTED]
>
>>> wrote:
>>>
>>> <snip>
>>>>
>>>>CHR$(PEEK(SADD(a$))) turns that ASCII value back
>>>>into a character and so the letter T will print.
>>>
>>> Ok, I see where you are going.
>>>
>>> Won't work with PDS or VBDOS far strings, as those strings are not in
>>> the "DEF SEG".
>>
>>With SSEG it does.  That's the beauty.  It returns the address of the 
>>string
>>as
>>an offset (near pointer) from the current data segment.  SADD can
>>be used with both near and far strings.  If the string is a far string,
>>use the SSEG function to determine its segment.
>>
>>a$ = "Test"
>>Segment = SSEG(a$)
>>Offset = SADD(a$)
>>DEF SEG = Segment
>>
>>? CHR$(PEEK(SADD(a$)))
>>will still print "T" no matter if a$ is near or far.
>
> All very true, but wouldn't "LEFT$(a$,1)" still be a lot easier?

Oh, you want *easy* do you?  8^)

My simple example was just to show how SSEG and SADD work.
In practice, you'd use those functions to store ML routines in the
string or to do string manipulation without fear of garbage
collection (just make sure you DON'T change the string length!)

Here's a more practical example:

To change "him" to "her" you could do this:

a$ = "him"
MID$(a$, 2) = "er"

but this would cause BASIC to make temp strings and
possibly move a$ around in memory. and trigger a garbage
collection.

If you do this:

a$ = "him"
Segment = SSEG(a$)
Offset = SADD(a$)
DEF SEG = Segment
POKE Offset + 1, ASC("e")
POKE Offset + 2, ASC("r")

This won't trigger garbage collection and is actually
faster than the MID$ method.

Tom Lake