Annotation of gforth/kernel/recognizer.fs, revision 1.19

1.1       pazsan      1: \ recognizer-based interpreter                       05oct2011py
                      2: 
                      3: \ Recognizer are words that take a string and try to figure out
                      4: \ what to do with it.  I want to separate the parse action from
                      5: \ the interpret/compile/postpone action, so that recognizers
                      6: \ are more general than just be used for the interpreter.
                      7: 
                      8: \ The "design pattern" used here is the *factory*, even though
                      9: \ the recognizer does not return a full-blown object.
                     10: \ A recognizer has the stack effect
                     11: \ ( addr u -- token table true | addr u false )
                     12: \ where the token is the result of the parsing action (can be more than
                     13: \ one stack or live on other stacks, e.g. on the FP stack)
                     14: \ and the table contains for actions (as array of four xts:
                     15: \ interpret it, compile interpretation semantics
                     16: \ compile it, compile it as literal.
                     17: 
1.7       pazsan     18: : recognizer: ( xt1 xt2 xt3 -- ) Create rot , swap , , ;
1.1       pazsan     19: 
1.7       pazsan     20: (field) r>int      ( r-addr -- addr )  0 cells ,
1.13      pazsan     21: (field) r>comp     ( r-addr -- addr )  1 cells ,
                     22: (field) r>lit      ( r-addr -- addr )  2 cells ,
1.1       pazsan     23: 
1.14      pazsan     24: ' no.extensions dup dup Create r:fail A, A, A,
                     25: 
1.15      pazsan     26: : lit, ( n -- ) postpone Literal ;
                     27: : nt, ( nt -- ) name>comp execute ;
1.18      pazsan     28: : nt-ex ( nt -- )
                     29:     [ cell 1 floats - dup [IF] ] lp+!# [ dup , [THEN] drop ]
                     30:     r> >l name>int execute @local0 >r lp+ ;
1.15      pazsan     31: 
1.16      pazsan     32: ' nt-ex
                     33: ' nt,
                     34: ' lit,
1.10      pazsan     35: Create r:word rot A, swap A, A,
1.1       pazsan     36: 
1.14      pazsan     37: : word-recognizer ( addr u -- nt r:word | addr u r:fail )
1.1       pazsan     38:     2dup find-name [ [IFDEF] prelude-mask ] run-prelude [ [THEN] ] dup
1.14      pazsan     39:     IF  nip nip r:word  ELSE  drop r:fail  THEN ;
1.1       pazsan     40: 
1.16      pazsan     41: ' noop
                     42: ' lit,
1.1       pazsan     43: dup
1.10      pazsan     44: Create r:num rot A, swap A, A,
1.1       pazsan     45: 
1.16      pazsan     46: ' noop
                     47: :noname ( n -- ) postpone 2Literal ;
1.1       pazsan     48: dup
1.10      pazsan     49: Create r:2num rot A, swap A, A,
1.7       pazsan     50: 
                     51: \ snumber? should be implemented as recognizer stack
1.1       pazsan     52: 
1.14      pazsan     53: : num-recognizer ( addr u -- n/d table | addr u r:fail )
1.1       pazsan     54:     2dup 2>r snumber?  dup
                     55:     IF
1.14      pazsan     56:        2rdrop 0> IF  r:2num   ELSE  r:num  THEN  EXIT
1.1       pazsan     57:     THEN
1.14      pazsan     58:     drop 2r> r:fail ;
1.3       pazsan     59: 
1.1       pazsan     60: \ recognizer stack
                     61: 
                     62: $10 Constant max-rec#
                     63: 
                     64: : get-recognizers ( rec-addr -- xt1 .. xtn n )
1.8       pazsan     65:     dup swap @ dup >r cells bounds swap ?DO
1.1       pazsan     66:        I @
1.8       pazsan     67:     cell -LOOP  r> ;
1.1       pazsan     68: 
                     69: : set-recognizers ( xt1 .. xtn n rec-addr -- )
                     70:     over max-rec# u>= abort" Too many recognizers"
1.8       pazsan     71:     2dup ! cell+ swap cells bounds ?DO
1.1       pazsan     72:        I !
1.8       pazsan     73:     cell +LOOP ;
1.1       pazsan     74: 
1.7       pazsan     75: Variable forth-recognizer
                     76: 
1.10      pazsan     77: ' word-recognizer A, ' num-recognizer A, max-rec# 2 - cells allot
1.7       pazsan     78: 2 forth-recognizer !
1.10      pazsan     79: \ ' num-recognizer ' word-recognizer 2 forth-recognizer set-recognizers
1.1       pazsan     80: 
                     81: \ recognizer loop
                     82: 
                     83: : do-recognizer ( addr u rec-addr -- token table )
                     84:     dup cell+ swap @ cells bounds ?DO
1.14      pazsan     85:        I perform dup r:fail <>  IF  UNLOOP  EXIT  THEN  drop
1.1       pazsan     86:     cell +LOOP
1.3       pazsan     87:     r:fail ;
1.1       pazsan     88: 
1.6       pazsan     89: \ nested recognizer helper
                     90: 
1.14      pazsan     91: \ : nest-recognizer ( addr u -- token table | addr u r:fail )
                     92: \   xxx-recognizer do-recognizer ;
1.6       pazsan     93: 
1.1       pazsan     94: : interpreter-r ( addr u -- ... xt )
1.16      pazsan     95:     forth-recognizer do-recognizer r>int @ ;
1.1       pazsan     96: 
1.7       pazsan     97: ' interpreter-r IS parser1
                     98: 
1.1       pazsan     99: : compiler-r ( addr u -- ... xt )
1.16      pazsan    100:     forth-recognizer do-recognizer r>comp @ ;
1.1       pazsan    101: 
                    102: : [ ( -- ) \  core     left-bracket
                    103:     \G Enter interpretation state. Immediate word.
                    104:     ['] interpreter-r  IS parser1 state off ; immediate
                    105: 
                    106: : ] ( -- ) \ core      right-bracket
                    107:     \G Enter compilation state.
                    108:     ['] compiler-r     IS parser1 state on  ;
                    109: 
1.16      pazsan    110: : >int      ( token table -- )  r>int perform ;
                    111: : >comp     ( token table -- )  r>comp perform ;
1.7       pazsan    112: : >postpone ( token table -- )
1.16      pazsan    113:     >r r@ r>lit perform r> r>comp @ compile, ;
1.7       pazsan    114: 
1.4       pazsan    115: : postpone ( "name" -- ) \ core
                    116:     \g Compiles the compilation semantics of @i{name}.
1.19    ! pazsan    117:     parse-name forth-recognizer do-recognizer >postpone
        !           118: ; immediate restrict
1.4       pazsan    119: 

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