Annotation of gforth/kernel/recognizer.fs, revision 1.17

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 ;
1.17    ! pazsan     28: : nt-ex ( nt -- )  r> >l name>int execute @local0 >r lp+ ;
1.15      pazsan     29: 
1.16      pazsan     30: ' nt-ex
                     31: ' nt,
                     32: ' lit,
1.10      pazsan     33: Create r:word rot A, swap A, A,
1.1       pazsan     34: 
1.14      pazsan     35: : word-recognizer ( addr u -- nt r:word | addr u r:fail )
1.1       pazsan     36:     2dup find-name [ [IFDEF] prelude-mask ] run-prelude [ [THEN] ] dup
1.14      pazsan     37:     IF  nip nip r:word  ELSE  drop r:fail  THEN ;
1.1       pazsan     38: 
1.16      pazsan     39: ' noop
                     40: ' lit,
1.1       pazsan     41: dup
1.10      pazsan     42: Create r:num rot A, swap A, A,
1.1       pazsan     43: 
1.16      pazsan     44: ' noop
                     45: :noname ( n -- ) postpone 2Literal ;
1.1       pazsan     46: dup
1.10      pazsan     47: Create r:2num rot A, swap A, A,
1.7       pazsan     48: 
                     49: \ snumber? should be implemented as recognizer stack
1.1       pazsan     50: 
1.14      pazsan     51: : num-recognizer ( addr u -- n/d table | addr u r:fail )
1.1       pazsan     52:     2dup 2>r snumber?  dup
                     53:     IF
1.14      pazsan     54:        2rdrop 0> IF  r:2num   ELSE  r:num  THEN  EXIT
1.1       pazsan     55:     THEN
1.14      pazsan     56:     drop 2r> r:fail ;
1.3       pazsan     57: 
1.1       pazsan     58: \ recognizer stack
                     59: 
                     60: $10 Constant max-rec#
                     61: 
                     62: : get-recognizers ( rec-addr -- xt1 .. xtn n )
1.8       pazsan     63:     dup swap @ dup >r cells bounds swap ?DO
1.1       pazsan     64:        I @
1.8       pazsan     65:     cell -LOOP  r> ;
1.1       pazsan     66: 
                     67: : set-recognizers ( xt1 .. xtn n rec-addr -- )
                     68:     over max-rec# u>= abort" Too many recognizers"
1.8       pazsan     69:     2dup ! cell+ swap cells bounds ?DO
1.1       pazsan     70:        I !
1.8       pazsan     71:     cell +LOOP ;
1.1       pazsan     72: 
1.7       pazsan     73: Variable forth-recognizer
                     74: 
1.10      pazsan     75: ' word-recognizer A, ' num-recognizer A, max-rec# 2 - cells allot
1.7       pazsan     76: 2 forth-recognizer !
1.10      pazsan     77: \ ' num-recognizer ' word-recognizer 2 forth-recognizer set-recognizers
1.1       pazsan     78: 
                     79: \ recognizer loop
                     80: 
                     81: : do-recognizer ( addr u rec-addr -- token table )
                     82:     dup cell+ swap @ cells bounds ?DO
1.14      pazsan     83:        I perform dup r:fail <>  IF  UNLOOP  EXIT  THEN  drop
1.1       pazsan     84:     cell +LOOP
1.3       pazsan     85:     r:fail ;
1.1       pazsan     86: 
1.6       pazsan     87: \ nested recognizer helper
                     88: 
1.14      pazsan     89: \ : nest-recognizer ( addr u -- token table | addr u r:fail )
                     90: \   xxx-recognizer do-recognizer ;
1.6       pazsan     91: 
1.1       pazsan     92: : interpreter-r ( addr u -- ... xt )
1.16      pazsan     93:     forth-recognizer do-recognizer r>int @ ;
1.1       pazsan     94: 
1.7       pazsan     95: ' interpreter-r IS parser1
                     96: 
1.1       pazsan     97: : compiler-r ( addr u -- ... xt )
1.16      pazsan     98:     forth-recognizer do-recognizer r>comp @ ;
1.1       pazsan     99: 
                    100: : [ ( -- ) \  core     left-bracket
                    101:     \G Enter interpretation state. Immediate word.
                    102:     ['] interpreter-r  IS parser1 state off ; immediate
                    103: 
                    104: : ] ( -- ) \ core      right-bracket
                    105:     \G Enter compilation state.
                    106:     ['] compiler-r     IS parser1 state on  ;
                    107: 
1.16      pazsan    108: : >int      ( token table -- )  r>int perform ;
                    109: : >comp     ( token table -- )  r>comp perform ;
1.7       pazsan    110: : >postpone ( token table -- )
1.16      pazsan    111:     >r r@ r>lit perform r> r>comp @ compile, ;
1.7       pazsan    112: 
1.4       pazsan    113: : postpone ( "name" -- ) \ core
                    114:     \g Compiles the compilation semantics of @i{name}.
1.7       pazsan    115:     parse-name forth-recognizer do-recognizer >postpone ; immediate
1.4       pazsan    116: 

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