Re: TIB: If-then-goto-end loops can create a problem
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Re: TIB: If-then-goto-end loops can create a problem
Somebody wrote:
> >>Using Goto statements in an If-Then-Else-End statement will cause
> >>the calc
> >>to gradually run out of mem because the End command will never
> >>be reached.
> >>The same applies to If-Then-End statements.
Yes, I think we've established this is true, and many of you have posted
example sections of code explaining how to get around it, yet these
conditional statements are specific to the programmer's game, and they will
figure out the best series of "If-Then" statments... Well, I have a theory as
to why the calc responds by slowing down or giving a memory error, when jumps
are made out of the conditional statements... The Basic program must make use
of the Stack within the RAM of the calculator, and it is frequently used in
ASM. The Stack is a structure that you can save values to, but mostly
addresses when you branch out to a subroutine, and then it removes the
address to know where to go after the subroutine is done. It has a "First In
/ Last Out" system, and I'll use the analogy of a stack of plates. If you put
a plate down, and one on top of it, you would have to remove the top plate
first to get to the one you put on first, right? Well, lets see how this
relates to Basic programs... If you had an "IF-Then" statement, and put
another "IF-Then" statment inside of it, the calc expects 2 "End" statements
to signify the stopping of that conditional. Well, that first "End" that it
encounters after both "IF-Then" Statements, cancels out the second "If-Then"
you made, not the first, yet the next "End" will cancel out the first one,
therefore showing the "Last-In / First Out " system... Anyways, back to why
"Goto" statements cause a problem. When a conditional statement is made,
there must be something that tells the calc to keep executing the commands
after an "IF-Then" statement only if that conditional was true. And when the
calc gets to an "End" statement, it knows to halt the conditional checking,
and remove that value or whatever from the Stack. If the program reaches a
"Goto" within the "IF-Then" statement, it will never get to that "End" and
keep pushing values down onto the stack upon every new "IF-Then" statment,
and if your program is doing those through a Loop, it will start building up.
I believe there is a set maximum for the number of values the calc can save
in its RAM on this stack structure, and once it reaches this limit, it will
give a memory error. The calc may slow down because it has difficult handling
all these conditionals and sorting them out... I dunno, Im just speculating
all of this due to my current level of ASM knowledge, but I doubt very few
people besides the people at TI, actually know what goes on during a Basic
program, involving the parser and translating all of these commands, its a
very difficult process. Hmm, im going to stop thinking about it so much.
Just y'all try avoid branching out of "IF-Then" statements with "Goto"s, it
will just suck for the calc after a while... =P
Jason_K - TCPA Member
http://tcpa.calc.org/
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