document for 4.3BSD release

SCCS-vsn: old/lex/PSD.doc/lex.ms 6.1

diff --git a/usr/src/old/lex/PSD.doc/lex.ms b/usr/src/old/lex/PSD.doc/lex.ms
index e85ba69..8b8bb0c 100644 (file)
--- a/usr/src/old/lex/PSD.doc/lex.ms
+++ b/usr/src/old/lex/PSD.doc/lex.ms
@@ -1,5 +1,7 @@
-.\"    @(#)lex.ms      5.1 (Berkeley) %G%
+.\"    @(#)lex.ms      6.1 (Berkeley) %G%

 .\"
 .\"

+.EH 'PS1:16-%''Lex \- A Lexical Analyzer Generator'
+.OH 'Lex \- A Lexical Analyzer Generator''PS1:16-%'

 .hc ~
 .bd I 2
 .de TS
 .hc ~
 .bd I 2
 .de TS


@@ -12,13 +14,13 @@
 .SP 1v
 .fi
 ..
 .SP 1v
 .fi
 ..

-.de PT
-.if \\n%>1 'tl ''\s7LEX\s0\s9\(mi%\s0''
-.if \\n%>1 'sp
-..
+.\".de PT
+.\".if \\n%>1 'tl ''\s7LEX\s0\s9\(mi%\s0''
+.\".if \\n%>1 'sp
+.\"..

 .ND July 21, 1975
 .ND July 21, 1975

-.RP
-.TM 75-1274-15 39199 39199-11
+.\".RP
+.\".TM 75-1274-15 39199 39199-11

 .TL
 Lex \- A Lexical Analyzer ~Generator~
 .AU ``MH 2C-569'' 6377
 .TL
 Lex \- A Lexical Analyzer ~Generator~
 .AU ``MH 2C-569'' 6377


@@ -28,10 +30,10 @@ M. E. Lesk and E. Schmidt
 .AB
 .sp
 .bd I 2
 .AB
 .sp
 .bd I 2

-.nr PS 8
-.nr VS 9
-.ps 8
-.vs 9p
+.\".nr PS 8
+.\".nr VS 9
+.\".ps 8
+.\".vs 9p

 Lex helps write programs whose control flow
 is directed by instances of regular
 expressions in the input stream.
 Lex helps write programs whose control flow
 is directed by instances of regular
 expressions in the input stream.


@@ -74,33 +76,9 @@ Lex is designed to simplify
 interfacing with Yacc, for those
 with access to this compiler-compiler system.
 ..
 interfacing with Yacc, for those
 with access to this compiler-compiler system.
 ..

-.nr PS 9
-.nr VS 11
+.\".nr PS 9
+.\".nr VS 11

 .AE
 .AE

-.SH
-.ce 1
-Table of Contents
-.LP
-.ce 100
-.TS
-r 1l 2r .
-1.     Introduction.   1
-2.     Lex Source.     3
-3.     Lex Regular Expressions.        3
-4.     Lex Actions.    5
-5.     Ambiguous Source Rules. 7
-6.     Lex Source Definitions. 8
-7.     Usage.  8
-8.     Lex and Yacc.   9
-9.     Examples.       10
-10.    Left Context Sensitivity.       11
-11.    Character Set.  12
-12.    Summary of Source Format.       12
-13.    Caveats and Bugs.       13
-14.    Acknowledgments.        13
-15.    References.     13
-.TE
-.ce 0

 .2C
 .NH
 Introduction.
 .2C
 .NH
 Introduction.


@@ -206,7 +184,6 @@ Input \(->  yylex   \(-> Output
 
 .sp
 An overview of Lex
 
 .sp
 An overview of Lex

-.sp

 Figure 1
 .TE
 .GE
 Figure 1
 .TE
 .GE


@@ -276,6 +253,8 @@ written by other generators
 or by hand, can
 be added easily to programs written by Lex.
 .BS 2
 or by hand, can
 be added easily to programs written by Lex.
 .BS 2

+.ps 9
+.vs 11

 .TS
 center;
 l c c c l
 .TS
 center;
 l c c c l


@@ -302,9 +281,10 @@ Input \(-> yylex   \(->    yyparse \(-> Parsed input
 
 .sp
        Lex with Yacc
 
 .sp
        Lex with Yacc

-.sp

        Figure 2
 .TE
        Figure 2
 .TE

+.ps 10
+.vs 12

 .BE
 Yacc users
 will realize that the name
 .BE
 Yacc users
 will realize that the name


@@ -1059,29 +1039,37 @@ text in various circumstances.  Consider the C problem of distinguishing
 the ambiguity of ``=\(mia''.
 Suppose it is desired to treat this as ``=\(mi a''
 but print a message.  A rule might be
 the ambiguity of ``=\(mia''.
 Suppose it is desired to treat this as ``=\(mi a''
 but print a message.  A rule might be

+.ps 9
+.vs 11

 .TS
 center;
 l l.
 =\(mi[a\-zA\-Z]        {
 .TS
 center;
 l l.
 =\(mi[a\-zA\-Z]        {

-       printf("Operator (=\(mi) ambiguous\en");
+       printf("Op (=\(mi) ambiguous\en");

        yyless(yyleng\-1);
        ... action for =\(mi ...
        }
 .TE
        yyless(yyleng\-1);
        ... action for =\(mi ...
        }
 .TE

+.ps 10
+.vs 12

 which prints a message, returns the letter after the
 operator to the input stream, and treats the operator as ``=\(mi''.
 Alternatively it might be desired to treat this as ``=  \(mia''.
 To do this, just return the minus
 sign as well as the letter to the input:
 which prints a message, returns the letter after the
 operator to the input stream, and treats the operator as ``=\(mi''.
 Alternatively it might be desired to treat this as ``=  \(mia''.
 To do this, just return the minus
 sign as well as the letter to the input:

+.ps 9
+.vs 11

 .TS
 center;
 l l.
 =\(mi[a\-zA\-Z]        {
 .TS
 center;
 l l.
 =\(mi[a\-zA\-Z]        {

-       printf("Operator (=\(mi) ambiguous\en");
+       printf("Op (=\(mi) ambiguous\en");

        yyless(yyleng\-2);
        ... action for = ...
        }
 .TE
        yyless(yyleng\-2);
        ... action for = ...
        }
 .TE

+.ps 10
+.vs 12

 will perform the other interpretation.
 Note that the expressions for the two cases might more easily
 be written
 will perform the other interpretation.
 Note that the expressions for the two cases might more easily
 be written


@@ -1423,8 +1411,11 @@ source is
 center;
 l l.
 %%
 center;
 l l.
 %%

-[a\-z][a\-z]   {digram[yytext[0]][yytext[1]]++; REJECT;}
-.      ;
+[a\-z][a\-z]   {
+       digram[yytext[0]][yytext[1]]++;
+       REJECT;
+       }
+\.     ;

 \en    ;
 .TE
 where the REJECT is necessary to pick up
 \en    ;
 .TE
 where the REJECT is necessary to pick up


@@ -1694,7 +1685,8 @@ l l.
        int k;
 \-?[0\-9]+     {
        k = atoi(yytext);
        int k;
 \-?[0\-9]+     {
        k = atoi(yytext);

-       printf("%d", k%7 == 0 ? k+3 : k);
+       printf("%d",
+         k%7 == 0 ? k+3 : k);

        }
 \-?[0\-9.]+    ECHO;
 [A-Za-z][A-Za-z0-9]+   ECHO;
        }
 \-?[0\-9.]+    ECHO;
 [A-Za-z][A-Za-z0-9]+   ECHO;


@@ -2215,7 +2207,8 @@ x+        1,2,3, ... instances of x.
 x|y    an x or a y.
 (x)    an x.
 x/y    an x but only if followed by y.
 x|y    an x or a y.
 (x)    an x.
 x/y    an x but only if followed by y.

-{xx}   the translation of xx from the definitions section.
+{xx}   the translation of xx from the
+       definitions section.

 x{m,n} \fIm\fR through \fIn\fR occurrences of x
 .TE
 .NH
 x{m,n} \fIm\fR through \fIn\fR occurrences of x
 .TE
 .NH