module lex.

accumulate scan.

type lparen, rparen, period, comma, backslash,
     truthtok, falsetok, negtok, andtok, ortok, imptok, 
     foralltok, existstok, lambdatok                         lex.
type tok             string -> lex.

% kind lex type.
% type white_space, in_symbol    int -> o.
% type single                    int -> lex -> o.
% type string_to_lex             string -> lex -> o.

white_space  9.          % tab
white_space 10.          % carrage return
white_space 12.          % form feed
white_space 32.          % space

in_symbol 35.           %  #
in_symbol 38.           %  &  
in_symbol 45.           %  -
in_symbol 58.           %  :
in_symbol 60.           %  <  
in_symbol 61.           %  =
in_symbol 62.           %  >  
in_symbol 63.           %  ?
in_symbol 64.           %  @
in_symbol 92.           %  \
in_symbol 95.           %  _
in_symbol C :- C > 47, C < 58.   % 0,1,...,9
in_symbol C :- C > 64, C < 91.   % A,B,...,Z
in_symbol C :- C > 96, C < 123.  % a,b,...,z

single 40 lparen.
single 41 rparen.
single 44 comma.
single 46 period.
single 47 backslash.

string_to_lex "forall" foralltok :- !.
string_to_lex "exists" existstok :- !.
string_to_lex "lambda" lambdatok :- !.
string_to_lex "neg"    negtok    :- !.
string_to_lex "truth"  truthtok  :- !.
string_to_lex "false"  falsetok  :- !.
string_to_lex "and"    andtok    :- !.
string_to_lex "or"     ortok     :- !.
string_to_lex "=>"     imptok    :- !.
string_to_lex Str      (tok Str).