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Diff for /src/usr.bin/lex/flex.1 between version 1.9 and 1.10

version 1.9, 2001/08/21 00:56:18

version 1.10, 2003/01/01 21:11:01

Line 393

Deficiencies / Bugs section below regarding

"dangerous trailing context".)

^r an r, but only at the beginning of a line (i.e.,

which just starting to scan, or right after a

just starting to scan, or right after a

newline has been scanned).

r$ an r, but only at the end of a line (i.e., just

before a newline). Equivalent to "r/\\n".

Line 617

.B yytext

(see the next section), and calls to the

.B unput()

function destroys the present contents of

function destroy the present contents of

.B yytext,

which can be a considerable porting headache when moving between different

.I lex

Line 1264

while in the first example it's active in both, because in the first

example the

.B example

startion condition is an

start condition is an

.I inclusive

.B (%s)

start condition.

Line 1383

.fi

This scanner goes to a bit of trouble to match as much

text as possible with each rule. In general, when attempting to write

a high-speed scanner try to match as much possible in each rule, as

a high-speed scanner try to match as much as possible in each rule, as

it's a big win.

.PP

Note that start-conditions names are really integer values and

Note that start-condition names are really integer values and

can be stored as such. Thus, the above could be extended in the

following fashion:

.nf

Line 1917

can be used to control whether the current buffer's scanning

context for the next token match is done as though at the

beginning of a line. A non-zero macro argument makes rules anchored with

'^' active, while a zero argument makes '^' rules inactive.

\'^' active, while a zero argument makes '^' rules inactive.

.PP

The macro

.B YY_AT_BOL()

Line 1928

switch statement and separated using

.B YY_BREAK,

which may be redefined. By default, it is simply a "break", to separate

each rule's action from the following rule's.

each rule's action from the following rules.

Redefining

.B YY_BREAK

allows, for example, C++ users to

Line 2452

scanner tables should be generated -

.I flex

should not compress the

tables by taking advantages of similar transition functions for

tables by taking advantage of similar transition functions for

different states.

.IP

.B \-CF

Line 3122

when it has scanned a token like "auto" and then the next character

is something other than a newline or a letter. Previously it would

then just match the "auto" rule and be done, but now it has no "auto"

rule, only a "auto\\n" rule. To eliminate the possibility of backing up,

rule, only an "auto\\n" rule. To eliminate the possibility of backing up,

we could either duplicate all rules but without final newlines, or,

since we never expect to encounter such an input and therefore don't

how it's classified, we can introduce one more catch-all rule, this

Line 3170

first way is to simply compile a scanner generated by

.I flex

using a C++ compiler instead of a C compiler. You should not encounter

any compilations errors (please report any you find to the email address

any compilation errors (please report any you find to the email address

given in the Author section below). You can then use C++ code in your

rule actions instead of C code. Note that the default input source for

your scanner remains

Line 3244

.B yy_delete_buffer(),

and

.B yyrestart()

(again, the first argument is a

(again, the first argument is an

.B istream*

object pointer).

.PP

Line 3268

respectively.

.TP

.B virtual int yylex()

performs the same role is

performs the same role as

.B yylex()

does for ordinary flex scanners: it scans the input stream, consuming

tokens, until a rule's action returns a value. If you derive a subclass

Line 3808

failed to notice the fact, meaning that

.I flex

scanned the first two sections looking for occurrences of these actions

and failed to find any, but somehow you snuck some in (via a #include

and failed to find any, but somehow you snuck some in (via an #include

file, for example). Use

.B %option reject