ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng)/ProfitPress-MegaCDROM2.B6I/MAGAZINE/MISC/AI_FEB87.ZIP/AIAPP.FEB

Text File | 1987-01-29 | 8.1 KB | 195 lines

                          AI Apprentice
                      Figures and Listings
               AI EXPERT magazine -- February 1987



                 |----------|     |----------|     |----------|
                 |   cons   |     |   cons   |     |   cons   |
                 |----------|     |----------|     |----------|
                 |      --------->|      --------> |      ----->NIL
                 |----------|     |----------|     |----------|
                 |          |     |          |     |          |
                 |----|-----|     |----|-----|     |----|-----|
                      |                |                |
                      V                V                V
                 |----------|     |----------|     |----------|
                 |  functor |     | constant |     | variable |
                 |----------|     |----------|     |----------|
                 |   likes  |     |  vicky   |     |  skiing  |
                 |----------|     |----------|     |----------|


Figure 1.
Linked list representation of "likes(vicky,skiing)."

  |----------|     |----------|     |----------|
  |   cons   |     |   cons   |     |   cons   |
  |----------|     |----------|     |----------|
  |      --------->|      --------> |      ----->NIL
  |----------|     |----------|     |----------|
  |          |     |          |     |          |
  |----|-----|     |----|-----|     |----|-----|
       |                |                |
       V                V                V
  |----------|     |----------|     |----------|    |---------|    |---------|
  |  functor |     | constant |     |   cons   |    |  cons   |    |  cons   |
  |----------|     |----------|     |----------|    |---------|    |---------|
  |   list   |     |    a     |     |      -------->|     -------->|    -------> NIL
  |----------|     |----------|     |----------|    |---------|    |---------|
                                    |          |    |         |    |         |
                                    |----|-----|    |----|----|    |----|----|
                                         |               |              |
                                         V               V              V
                                    |----------|    |---------|    |---------|
                                    |  functor |    | constant|    | constant|
                                    |----------|    |---------|    |---------|
                                    |  list    |    |    b    |    |   nil   |
                                    |----------|    |---------|    |---------|

Figure 2
The internal representation of list(a,list(b,nil)).



     sentence ::- rule | query | command
     rule ::- head '.' | head ':-' tail '.'
     query ::- '?-' tail '.'
     command ::- '@' file_name '.'
     head ::- goal
     tail ::- goal | goal ',' tail
     goal ::- constant | variable | structure
     constant ::- {quoted string} | {token beginning with 'a' .. 'z'}
     variable ::- {identifier beginning with 'A' .. 'Z' or '_' }
     structure ::- functor '(' component_list ')'
     functor ::- {token beginning with 'a' .. 'z'}
     component_list ::- term | term ',' component_list
     term ::- goal | list
     list ::- '[]' | '[' element_list ']'
     element_list ::- term | term ',' element_list | term | term
     file_name ::- {legitimate DOS file name, must be surrounded with
                    single quotes if it contains a '.',':' or '\'}


Figure 3
VTPROLOG Grammar.


      PROCEDURE list(VAR l_ptr : node_ptr) ;
       VAR
        elem_list : node_ptr ;

       PROCEDURE element_list(VAR e_list : node_ptr) ;
        VAR
         e_list2 : node_ptr ;
        BEGIN
         term(e_list) ;
         IF token = ','
          THEN
           BEGIN
            scan(source,token) ;
            element_list(e_list) ;
           END
         ELSE IF token = '|'
          THEN
           BEGIN
            e_list2 := NIL ;
            scan(source,token) ;
            term(e_list2) ;
            e_list := append_list(e_list,head(e_list2)) ;
           END ;
        END ; (* element_list *)

       BEGIN
        scan(source,token) ;
        IF token = ']'
         THEN
          BEGIN
           l_ptr := append_list(l_ptr,cons(NIL,NIL)) ;
           scan(source,token) ;
          END
         ELSE
          BEGIN
           elem_list := NIL ;
           element_list(elem_list) ;
           IF token = ']'
            THEN
             BEGIN
              scan(source,token) ;
              l_ptr := append_list(l_ptr,cons(elem_list,NIL)) ;
             END
            ELSE error('Missing '']''.') ;
          END ;
       END ; (* list *)

Figure 4
A routine to recognize lists.

              |----------|     |----------|     |----------|
              |   cons   |     |   cons   |     |   cons   |
              |----------|     |----------|     |----------|
              |      --------->|      --------> |      ----->NIL
              |----------|     |----------|     |----------|
              |          |     |          |     |          |
              |----|-----|     |----|-----|     |----|-----|
                   |                |                |
                   V                V                V
              |----------|     |----------|     |----------|
              | constant |     | constant |     | constant |
              |----------|     |----------|     |----------|
              |    a     |     |    b     |     |    c     |
              |----------|     |----------|     |----------|

Figure 5
The internal representation of [a,b,c].

              |----------|     |----------|     |----------|
              |   cons   |     |   cons   |     | variable |
              |----------|     |----------|     |----------|
              |      --------->|      --------> |    Z     |
              |----------|     |----------|     |----------|
              |          |     |          |
              |----|-----|     |----|-----|
                   |                |
                   V                V
              |----------|     |----------|
              | variable |     | variable |
              |----------|     |----------|
              |    X     |     |    Y     |
              |----------|     |----------|

Figure 6
The internal structure of [X,Y|Z].


item     |     Item within the query
in the   |
rule     |     constant       variable       functor            list
         |      (C2)           (V2)           (F2)              (L2)
         |--------------------------------------------------------------------
constant |     succeed if     succeed        fail               fail
(C1)     |     C1 = C2        bind V2 to C1
         |
variable |     succeed        succeed        succeed            succeed
(V1)     |     bind V1 to C2  bind V1 to V2  bind V1 to F2      bind V1 to L2
         |
functor  |     fail           succeed        succeed if         fail
(F1)     |                    bind V2 to F1  expressions have
         |                                   same functor and
         |                                   arity and each
         |                                   of components
         |                                   can be unified
         |
list     |     fail           succeed        fail               succeed if
(L1)     |                    bind V2 to L1                     heads can be unified
         |                                                      and tails can be
         |                                                      unified

Table 1
Unification table for rules and queries.

        |                                                      unified

Table 1
Unification table for rules and queri