用Perl编写的一个小的词法分析器

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#++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#
#	@File  ： Lexical_Analyzer.pl
#	@Author： Roc
#	@Date  ： 2013/10/21
#	@Func  ： Lexical analyser
#	@Idea  :  In this program，we cut sentences to words.
#			  Then,we will match each word.
#
#++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#!/usr/bin/perl
use warnings;
use 5.010;

say "Please input your program here.(Input '__END__' to stop inputing)";

##
#input here
#
open (FH,">LexicalAnalyser.txt") or die "can't open the file: $!";
while (<STDIN>) {
	if (/__END__/){
		#Input over.Close file 
		close (FH) or die "Can't close file: $!";
		last;	#Interrupt here
	} else {	
		#debug
		#print "I saw $_";
		chomp ($_);	#delete 'Enter'
		say FH $_;

	}
} #End of while

##
#output program here.We just test our input.
#
$count = 1;
say "n+------------------------------------------------+";
say "tInput over.Here is your program.n";
#
#Read file here.
#We just want to see if we write into the file
#
open (FH,"<LexicalAnalyser.txt") or die "can't open the file: $!";
foreach (<FH>) {
	chomp;
	say "Line $count: $_";
	$count++;
}
say "+------------------------------------------------+n";
close (FH) or die "can't close file: $!";
#debug
#say "@Tmpn";


##
#Exchange special flags here.I just list a little:like,} { ) ( and ;
#
open (FH,"<LexicalAnalyser.txt") or die "can't open the file: $!";
foreach (<FH>){
	foreach (split){
		#debug
		#print "!!!!!!!!!!!!!!!!!!!!n";
		
		#We have already separated each word.
		#Thus,it doesn't matter if we add g here.
		s/(w+)(,|;|)|(|}|{)/$1 $2/g;
		s/(,|;|(|)|{|}|:|[|])(w+)/$1 $2/g;
		s/(;|(|)|{|})/ $1/g;
		#Store in Tmp2
		push @Tmp2,$_;
	}
}
close (FH) or die "can't close file: $!";


##
#We match here
#
foreach (@Tmp2){
	#debug
	#say "$_";
 foreach (split){
	 #debug
	 #print "!!!!!!!!!!!!!!!!!!!!n";
	 if ($_ =~ /main()/){
		 push @Tmp3,"(2,"main")";
     } elsif ($_ =~ /(int|float|for|while|do|return|break|continue|unsigned|public|void)/){
		 push @Tmp3,"(1,"$_")";
	 } elsif ($_ =~ /[a-z]+/){
		 push @Tmp3,"$_")";
	 } elsif ($_ =~ /p{Digit}.*/){
   		 push @Tmp3,"(3,"$_")";
     } elsif ($_ =~ /(=|>=|<=|!=|!|>|<|+|-|*|/)/){
		 push @Tmp3,"(4,"$_")";
	 } elsif ($_ =~ /((|)|{|}|;|,|:)/){
		 push @Tmp3,"(5,"$_")";
	 }
	 #debug
	 #print "$_n";
	# push @Tmp1,$_;    #再设置一个暂存区
  } #End of foreach(split)
} #End of foreach(@Tmp2)

##
#Output here
#
say "++++++++++++Final Answer+++++++++++";
say "-----------------------------------";
foreach (@Tmp3){
	say "$_";
}
say "+---------------------------------+";
say "+++++++++++++++END+++++++++++++++++";

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