On 8/15/10 10:33 PM, Standish P wrote:
...
I don't understand a lot of your post (and it's clear that I'm not
alone). I don't know whether it's a (human) language problem or simply
an issue of your having read too many books and not having enough
practical experience, but at least I can try to address the Forth questions.
If Forth is a general processing language based on stack, is it
possible to convert any and all algorithms to stack based ones and
thus avoid memory leaks since a pop automatically releases memory when
free is an intrinsic part of it.
Forth uses two stacks. The "data stack" is used for passing parameters
between subroutines ("words") and is completely under the control of the
programmer. Words expect parameters on this stack; they remove them,
and leave only explicit results. The "return stack" is used primarily
for return addresses when words are called, although it is also
available for auxiliary uses under guidelines which respect the primary
use for return addresses.
Although implementations vary, in most Forths stacks grow from a fixed
point (one for each stack) into otherwise-unused memory. The space
involved is allocated when the program is launched, and is not managed
as a heap and allocated or deallocated by any complicated mechanism. On
multitasking Forth systems, each task has its own stacks. Where
floating point is implemented (Forth's native arithmetic is
integer-based), there is usually a separate stack for floats, to take
advantage of hardware FP stacks.
- is forth a general purpose language? Yes
- are all algorithms stack based? No
Does Forth uses stack for all algorithms ? Does it use pointers , ie
indirect addressing ? If it can/must use stack then every algorithm
could be made stack based.
Forth uses its data stack for parameter passing and storage of temporary
values. It is also possible to define variables, strings, and arrays in
memory, in which case their addresses may be passed on the data stack.
Forth is architecturally very simple. Memory allocations for variables,
etc., are normally static, although some implementations include
facilities for heaps as needed by applications.
Hope this helps. If you are interested in learning more about Forth,
there are several books available (try Amazon). Get one of the more
recent ones, some of which I wrote.
Cheers,
Elizabeth
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applications since 1973."
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