On Aug 28, 2012, at 2:50 AM, openbios-request(a)openbios.org wrote:
Date: Mon, 27 Aug 2012 21:18:08 -0400
From: Tarl Neustaedter <tarl-b2(a)tarl.net>
To: The OpenBIOS Mailinglist <openbios(a)openbios.org>
Subject: Re: [OpenBIOS] [PATCH] Adds local variable support to
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And don't use CamelCase.
Is this some official naming convention, or your own taste?
In general (at least in the 1275 world), Forth is case-insensitive. The
rare cases where it is made case sensitive (there are a couple in Sun's
Openboot - see dropins.src) make use of mixed case very painful. The
general standard is that methods and variables are lower case, defined
constants and structure offsets are upper case. In some code, even they
are lower case.
Mixed-case is generally confined to comments.
Are you saying my-variable is better than myVariable?
this? You shouldn't ever use a variable that is used as a temp
inside a word.
I'm not sure why you suggest this. It is just such a pain having to
deal with the stack.
Because using a global variable gets you in trouble in recursion or when
the same code is called at alarm level. As for stack being a pain, yes,
that's forth. Stack manipulation as a way of life. Personally, I prefer
"2over nip" rather than "2 pick" :-)
How do global variables get you in trouble in recursion? Do you have an example?
I am not familiar with this alarm level. Could you explain what it is?
+48 CONSTANT localTableSize
+\ Declare the local variable table
+localTableSize ARRAY localVariableTable
You have 48 but can only access 12?
That is four fields per local variable: 48 / 4 = 12.
At a minimum, any derived constants should be derived explicitly. Like:
12 constant #local-variables \ Feels right. If you need more, add
more code after Locals11.
4 constant /local-variable \ Datastructures require four cells
#local-variables /local-variable * constant locals-table-size \ Size in
cells, not bytes.
Ah. That points out another convention. When mashing together multiple
words for a method or variable name, we tend to use dashes as separators
(and please, don't use underscores. There is someone I know who *mixes*
underscores and dashes in variable names!). Another is that sizes of
things are usually /object (such as /n, /l, ...) and counts of objects
are usually #object.
Ok. Sounds reasonable.
+arrayCount 4 /
Oh. Use a struct?
The little documentation on struct I found did not indicate it was a
better replacement for Array.
Struct will allow you define what the four separate words used in each
local variable entry are used for. If you use structs, I'd expect to see
/n field >LOCAL-INIT
/n field >LOCAL-ORDER
/n field >LOCAL-LEN
/n field >LOCAL-ADDR
12 constant #local-variables
/local-variable #local-variables constant locals-table-size
Note that the above provides the table size in bytes, rather than cells.
To use the above (assuming you are still using alloc-mem), you'd see
locals-table-size alloc-mem ( table )
#local-variables 0 do ( table )
i /local-variable * ( table entry )
0 over >LOCAL-INIT ! ( table entry )
0 over >LOCAL-ORDER ! ( table entry )
0 over >LOCAL-LEN ! ( table entry )
0 swap >LOCAL-ADDR ! ( table )
loop ( table )
That looks very unfriendly. There is no way I am using structs.