Annotation of gforth/kernel/recognizer.fs, revision 1.16

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 ;
1.16    ! pazsan     28: Variable nt-ex-r
        !            29: : nt-ex ( nt -- )  r> nt-ex-r ! name>int execute nt-ex-r @ >r ;
1.15      pazsan     30: 
1.16    ! pazsan     31: ' nt-ex
        !            32: ' nt,
        !            33: ' lit,
1.10      pazsan     34: Create r:word rot A, swap A, A,
1.1       pazsan     35: 
1.14      pazsan     36: : word-recognizer ( addr u -- nt r:word | addr u r:fail )
1.1       pazsan     37:     2dup find-name [ [IFDEF] prelude-mask ] run-prelude [ [THEN] ] dup
1.14      pazsan     38:     IF  nip nip r:word  ELSE  drop r:fail  THEN ;
1.1       pazsan     39: 
1.16    ! pazsan     40: ' noop
        !            41: ' lit,
1.1       pazsan     42: dup
1.10      pazsan     43: Create r:num rot A, swap A, A,
1.1       pazsan     44: 
1.16    ! pazsan     45: ' noop
        !            46: :noname ( n -- ) postpone 2Literal ;
1.1       pazsan     47: dup
1.10      pazsan     48: Create r:2num rot A, swap A, A,
1.7       pazsan     49: 
                     50: \ snumber? should be implemented as recognizer stack
1.1       pazsan     51: 
1.14      pazsan     52: : num-recognizer ( addr u -- n/d table | addr u r:fail )
1.1       pazsan     53:     2dup 2>r snumber?  dup
                     54:     IF
1.14      pazsan     55:        2rdrop 0> IF  r:2num   ELSE  r:num  THEN  EXIT
1.1       pazsan     56:     THEN
1.14      pazsan     57:     drop 2r> r:fail ;
1.3       pazsan     58: 
1.1       pazsan     59: \ recognizer stack
                     60: 
                     61: $10 Constant max-rec#
                     62: 
                     63: : get-recognizers ( rec-addr -- xt1 .. xtn n )
1.8       pazsan     64:     dup swap @ dup >r cells bounds swap ?DO
1.1       pazsan     65:        I @
1.8       pazsan     66:     cell -LOOP  r> ;
1.1       pazsan     67: 
                     68: : set-recognizers ( xt1 .. xtn n rec-addr -- )
                     69:     over max-rec# u>= abort" Too many recognizers"
1.8       pazsan     70:     2dup ! cell+ swap cells bounds ?DO
1.1       pazsan     71:        I !
1.8       pazsan     72:     cell +LOOP ;
1.1       pazsan     73: 
1.7       pazsan     74: Variable forth-recognizer
                     75: 
1.10      pazsan     76: ' word-recognizer A, ' num-recognizer A, max-rec# 2 - cells allot
1.7       pazsan     77: 2 forth-recognizer !
1.10      pazsan     78: \ ' num-recognizer ' word-recognizer 2 forth-recognizer set-recognizers
1.1       pazsan     79: 
                     80: \ recognizer loop
                     81: 
                     82: : do-recognizer ( addr u rec-addr -- token table )
                     83:     dup cell+ swap @ cells bounds ?DO
1.14      pazsan     84:        I perform dup r:fail <>  IF  UNLOOP  EXIT  THEN  drop
1.1       pazsan     85:     cell +LOOP
1.3       pazsan     86:     r:fail ;
1.1       pazsan     87: 
1.6       pazsan     88: \ nested recognizer helper
                     89: 
1.14      pazsan     90: \ : nest-recognizer ( addr u -- token table | addr u r:fail )
                     91: \   xxx-recognizer do-recognizer ;
1.6       pazsan     92: 
1.1       pazsan     93: : interpreter-r ( addr u -- ... xt )
1.16    ! pazsan     94:     forth-recognizer do-recognizer r>int @ ;
1.1       pazsan     95: 
1.7       pazsan     96: ' interpreter-r IS parser1
                     97: 
1.1       pazsan     98: : compiler-r ( addr u -- ... xt )
1.16    ! pazsan     99:     forth-recognizer do-recognizer r>comp @ ;
1.1       pazsan    100: 
                    101: : [ ( -- ) \  core     left-bracket
                    102:     \G Enter interpretation state. Immediate word.
                    103:     ['] interpreter-r  IS parser1 state off ; immediate
                    104: 
                    105: : ] ( -- ) \ core      right-bracket
                    106:     \G Enter compilation state.
                    107:     ['] compiler-r     IS parser1 state on  ;
                    108: 
1.16    ! pazsan    109: : >int      ( token table -- )  r>int perform ;
        !           110: : >comp     ( token table -- )  r>comp perform ;
1.7       pazsan    111: : >postpone ( token table -- )
1.16    ! pazsan    112:     >r r@ r>lit perform r> r>comp @ compile, ;
1.7       pazsan    113: 
1.4       pazsan    114: : postpone ( "name" -- ) \ core
                    115:     \g Compiles the compilation semantics of @i{name}.
1.7       pazsan    116:     parse-name forth-recognizer do-recognizer >postpone ; immediate
1.4       pazsan    117: 

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