Hi all,
I wanted to discuss a little trick I implemented a few days ago.
In the new code generator I'm working on, there are various data types
representing virtual instructions. For example,
TUPLE: %call < insn word ;
TUPLE: %jump < insn word ;
TUPLE: %intrinsic < insn quot vregs ;
TUPLE: %return < insn ;
What I do is wrap a bunch of code in a 'make' form and build a
sequence of such instructions by traversing the high level IR.
For example, we might generate a call to '+' as follows,
\ + %call boa ,
However, this is a bit repetitive, so we might try factoring it out:
: %call ( word -- ) \ %call boa , ;
However, doing this for each instruction is tedious, and so is
specifying the superclass for each one. So I made a parsing word INSN:
INSN: %call word ;
INSN: %jump word ;
INSN: %intrinsic quot vregs ;
INSN: %return ;
Here is the implementation:
: INSN:
parse-tuple-definition
[ dup tuple eq? [ drop insn ] when ] dip
[ define-tuple-class ]
[ 2drop save-location ]
[ 2drop dup [ boa , ] curry define-inline ]
3tri ; parsing
It's a bit long, but it saves more code than it consumes.
Also 'make' is ideal here. I have instruction generation spread out
over many words. 'bake' doesn't apply here and passing a vector around
on the stack or in a local variable will get tedious very quickly. It
is also nice that the call to 'boa ,' can be hidden in a word with the
same name as the class.
Finally, for instructions with no parameters, eg %return, the
optimizer folds the 'boa' call at compile time (it actually does it
for tuples where all slots are read-only, of which empty tuples are a
special case of course). So, INSN: %return ; becomes something like
TUPLE: %return < insn ;
: %return ( -- ) T{ %return } , ; inline
Very nice.
I like programming in Factor. There's nothing else out there that
offers the unique mix of capabilities that Factor has.
Slava
-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Factor-talk mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/factor-talk
