\ recognizer-based interpreter 05oct2011py
\ Recognizer are words that take a string and try to figure out
\ what to do with it. I want to separate the parse action from
\ the interpret/compile/postpone action, so that recognizers
\ are more general than just be used for the interpreter.
\ The "design pattern" used here is the *factory*, even though
\ the recognizer does not return a full-blown object.
\ A recognizer has the stack effect
\ ( addr u -- token table true | addr u false )
\ where the token is the result of the parsing action (can be more than
\ one stack or live on other stacks, e.g. on the FP stack)
\ and the table contains for actions (as array of four xts:
\ interpret it, compile interpretation semantics
\ compile it, compile it as literal.
: recognizer: ( xt1 xt2 xt3 xt4 -- ) Create 2swap swap 2, swap 2, ;
(field) r>int ( r-addr -- addr ) 0 cells ,
(field) r>compint ( r-addr -- ) 1 cells ,
(field) r>comp ( r-addr -- ) 2 cells ,
(field) r>lit ( r-addr -- ) 3 cells ,
:noname ( ... nt -- ) name>int execute ;
:noname ( ... nt -- ) name>int compile, ;
:noname ( ... nt -- ) name>comp execute ;
:noname ( ... nt -- ) postpone Literal ;
recognizer: r:int-table
:noname ( addr u -- nt int-table true | addr u false )
2dup find-name [ [IFDEF] prelude-mask ] run-prelude [ [THEN] ] dup
IF
nip nip r:int-table true EXIT
THEN ; Constant int-recognizer
' noop
:noname postpone Literal ;
dup
dup
recognizer: r:number
' noop
:noname postpone 2Literal ;
dup
dup
recognizer: r:2number
:noname ( addr u -- nt int-table true | addr u false )
2dup 2>r snumber? dup
IF
2rdrop 0> IF r:2number ELSE r:number THEN true EXIT
THEN
drop 2r> false ; Constant num-recognizer
\ recognizer stack
$10 Constant max-rec#
Variable forth-recognizer max-rec# cells allot
: get-recognizers ( rec-addr -- xt1 .. xtn n )
dup cell+ swap @ dup >r cells bounds ?DO
I @
cell +LOOP r> ;
: set-recognizers ( xt1 .. xtn n rec-addr -- )
over max-rec# u>= abort" Too many recognizers"
2dup ! swap cells bounds swap ?DO
I !
cell -LOOP ;
num-recognizer int-recognizer 2 forth-recognizer set-recognizers
\ recognizer loop
: do-recognizer ( addr u rec-addr -- token table )
dup cell+ swap @ cells bounds ?DO
I perform IF UNLOOP EXIT THEN
cell +LOOP
no.extensions ;
: interpreter-r ( addr u -- ... xt )
forth-recognizer do-recognizer r>int @ ;
: compiler-r ( addr u -- ... xt )
forth-recognizer do-recognizer r>comp @ ;
: [ ( -- ) \ core left-bracket
\G Enter interpretation state. Immediate word.
['] interpreter-r IS parser1 state off ; immediate
: ] ( -- ) \ core right-bracket
\G Enter compilation state.
['] compiler-r IS parser1 state on ;
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