LEX(1)

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LEX(1)

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lex - ��

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   lex  [-r] [-c] [-t] [-v] [-n] [���� ...]

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�� lex �� , �� .

�� (�� - �� ) �� , �� , � �� C, �� .

�� lex.yy.c. �� , �� C-��, � �� . �� yytext. �� , � �� . �� , �� (��, [abx-z] �� a, b, x, y � z), � �� *, + � ?, �� , ��, �� , �� , 0 �� . �� . - �� ASCII, �� . � ��, �� (�� ) � �� (��). �� r{d,e} � �� r �� d � e. �� , �� |, �� , �� *, ?, + � ��. �� ^ � �� , �� , �� $ � �� , �� . �� / � �� , �� yytext, �� . �� , �� \. ��: �� [a-zA-Z]+ �� .

�� : input( ) - �� ; unput(c) - �� ; output(c) - �� . �� , �� . �� -�� yylex( ), �� main( ), �� . �� REJECT � �� ; �� yymore( ) �� yytext; �� yyless(p) �� , �� p, �� yytext � yytext+yyleng. �� input � output �� yyin � yyout �� (�� stdin � stdout ��).

��, �� , �� C � �� lex.yy.c; �� %%, �� lex.yy.c. �� , �� YACC, �� %%. ��, �� %% � �� , �� ; �� , �� { }. ��, �� .

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     D       [0-9]
     %%
     if      printf("IF statement\n");
     [a-z]+  printf("tag, value %s\n",yytext);
     0{D}+   printf("octal number %s\n",yytext);
     {D}+    printf("decimal number %s\n",yytext);
     "++"    printf("unary op\n");
     "+"     printf("binary op\n");
     "/*"     skipcommnts();
     %%
      skipcommnts()
      {
        for(;;) {
          while (input() != '*')
            ;
          if (input() != '/')
            unput(yytext[yyleng-1]);
          else
            return;
        }
      }

�� , �� lex, �� yy �� YY.

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-r �� ratfor [��. ratfor(1)].
-c �� C (�� ).
-t �� lex.yy.c.
-v �� .
-n �� .

-r	�� ratfor [��. ratfor(1)].
-c	�� C (�� ).
-t	�� lex.yy.c.
-v	�� .
-n	�� .

�� , �� . �� , �� .

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%p n �� n (�� - 2500)
%n n �� (500)
%e n �� (1000)
%a n �� (2000)
%k n �� (1000)
%o n �� (3000)

�� -v, �� -n.

��. ��
yacc(1).

%p n	�� n (�� - 2500)
%n n	�� (500)
%e n	�� (1000)
%a n	�� (2000)
%k n	�� (1000)
%o n	�� (3000)