BBC BASIC for Windows - Double LOCAL

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Double LOCAL

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Matt
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Re: Double LOCAL
« Reply #2 on: Nov 23^rd, 2013, 05:27am »

on Nov 22^nd, 2013, 08:36am, Richard Russell wrote:

In LOCAL A% the LOCAL means that the variable A% should be saved temporarily during the execution of the FN/PROC, and restored on exit, so that it does not affect the use of that same variable in the code from which the FN/PROC is called.

In DIM A% LOCAL 67 the LOCAL means that the memory is allocated from the stack rather than from the heap. Memory allocated from the stack is freed when the FN/PROC exits, but memory allocated from the heap isn't.

OK. That makes sense. But does that mean that DIM A% 67 allocates memory from the heap and therefore isn't freed on exit from a FN/PROC?

Matt

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Re: Double LOCAL
« Reply #3 on: Nov 23^rd, 2013, 09:50am »

on Nov 23^rd, 2013, 05:27am, Matt wrote:

But does that mean that DIM A% 67 allocates memory from the heap and therefore isn't freed on exit from a FN/PROC?

Absolutely. That doesn't mean one would never use it in a FN/PROC however. For example in the linked list article a FN is used to create a new node:

Code:

      DEF FNnewnode(RETURN n{})
      LOCAL P%
      DIM P% DIM(n{})-1
      !(^n{}+4) = P%
      = P%

Here it's obviously correct that the memory block is allocated from the heap and not freed on exit.

Richard.

« Last Edit: Nov 23^rd, 2013, 09:50am by admin »

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