Difference between revisions of "Extraordinary String Animals"

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interpreter recognizes the difference between an ordinary $tring animal and
 
interpreter recognizes the difference between an ordinary $tring animal and
 
an "extraordinary" $tring animal.  Offhand, I don't have a concrete answer.
 
an "extraordinary" $tring animal.  Offhand, I don't have a concrete answer.
Whenever I have occassion to create "extraordinary" $tring animals, most of
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Whenever I have occasion to create "extraordinary" $tring animals, most of
 
the time they are of very substantial LENgth yet there is no operational
 
the time they are of very substantial LENgth yet there is no operational
 
program activity that would amount to exposure to "garbage collection"
 
program activity that would amount to exposure to "garbage collection"
 
events.  However, I dimly recall investigating the question a long time ago.
 
events.  However, I dimly recall investigating the question a long time ago.
 
As I recall, I was delighted and surprised to discover that the BASIC
 
As I recall, I was delighted and surprised to discover that the BASIC
interpreter does recognize the difference between an ordinary $tring animals
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interpreter does recognize the difference between ordinary $tring animals
and an "extraordinary" $tring animals such that the potential for, and manag
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and "extraordinary" $tring animals such that the potential for, and management of, "garbage collection" events is not impacted by the existence of
ement of, "garbage collection" events is not impacted by the existance of
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"extraordinary" $tring animals.  At least that's what I recall.  My
 
"extraordinary" $tring animals.  At least that's what I recall.  My
 
recollection likely is accurate given how the BASIC interpreter already
 
recollection likely is accurate given how the BASIC interpreter already

Revision as of 07:28, 2 March 2009

Ron Wiesen, in response to a question from Wilson Van Alst:

To your first question: the situation of $trings (i.e., where they sit) in the $tring-space can set the stage for a compelled 'garbage collection' that takes place, as a neccessary prelude, to a subsequent $tring operation. In other words, the $tring-space holds existing $trings which are not adjoined (unused gaps of space are between $trings) and then the BASIC interpreter encounters some $tring operation. The total volume of unused $tring-space is sufficient to support the $tring operation. But that total is fragmented due to the way existing $trings are situated in the $tring-space. This compels the BASIC interpreter to suspend interpretation, conduct 'garbage collection' in order to consolidate the unused volume into one contiguous span, and then continue with interpretation -- performing the $tring operation.

To your second question: you've overlooked the "extraordinary" $tring animals. These creatures begin their life born as ordinary $tring animals (typically 0-length nuls). They then mutate into "extraordinary" $tring animals of some finite (often substantial) length. What makes these creatures "extraordinary" $tring animals is that their related $tring content is ROM-based (not RAM-based in the the $tring-space). Below is an example of how an "extraordinary" $tring animal is brought into existance.

E%=32676:E$="":
POKE0+VARPTR(E$),25:POKE1+VARPTR(E$),E%MOD256:POKE2+VARPTR(E$),E%\256

E$ was born as an ordinary $tring animal with a LENgth of 0 (nul). In the ROM-space, address 32676 is the locale of a 25-cell that holds a bunch of values that are ASCII character codes.

Note that the $tring variable called E$, like any other type of variable, lives in the variable-space within RAM. In the case of a $tring variable, the variable-space holds two attributes: LENgth, and Address_of_content. The function VARPTR, as applied to a $tring variable, returns the locale of the LENght attribute. So 0+VARPTR(E$) is the locale for LENgth of the $tring variable called E$. In the variable-space for a $tring variable, the LENgth attribute is immediately followed by the Address_of_content attribute. So 1+VARPTR(E$) and 2+VARPTR(E$), respectively, are the Least significant and the Most significant halves of the locale for Address_of_content of the $tring variable called E$. Via three POKEs, the creature called E$ mutates into an "extraordinary" $tring animal.

Sure, go ahead. Do a PRINT E$ statement in order to discover what the ROM-based content looks like (you can't resist the temptation).

What makes the "extraordinary" $tring animals so extraordinary in contrast to ordinary $tring animals? Although both of these creatures live in the variable-space, as do creatures of all variable types, they obtain their runs of character codes from radically different media. The ordinary $tring animal "feeds" from RAM media: within a BASIC statement in the case of "literal" food, or within the $tring-space in the case of changeable food. The "extraordinary" $tring animal "feeds" from ROM media where all food is "literal" in the sense that it's cast in stone (i.e., silicon).

To your third question: you've overlooked whether or not the BASIC interpreter recognizes the difference between an ordinary $tring animal and an "extraordinary" $tring animal. Offhand, I don't have a concrete answer. Whenever I have occasion to create "extraordinary" $tring animals, most of the time they are of very substantial LENgth yet there is no operational program activity that would amount to exposure to "garbage collection" events. However, I dimly recall investigating the question a long time ago. As I recall, I was delighted and surprised to discover that the BASIC interpreter does recognize the difference between ordinary $tring animals and "extraordinary" $tring animals such that the potential for, and management of, "garbage collection" events is not impacted by the existence of "extraordinary" $tring animals. At least that's what I recall. My recollection likely is accurate given how the BASIC interpreter already recognizes those ordinary $tring animals that have "literal" food in a BASIC statement -- to the BASIC interpreter, those creatures perhaps "look the same as" any existing "extraordinary" $tring animals with respect to "garbage collection" considerations.