use strict;
use warnings;
package DFA;

my $dfa = {
    start         =>{nextstate =>{s      =>'var1_1orfun1_1'},
                     entrytoken=>'OTHER'},
    var1_1orfun1_1=>{nextstate =>{i      =>'var1_2orfun1_2'}},
    var1_2orfun1_2=>{exittoken =>{n      =>'',
                                  default=>'ARG'},
                     nextstate =>{n      =>'fun1_3',
                                  s      =>'var1_1orfun1_1'}},
    fun1_3        =>{nextstate =>{'('    =>'fun1_4'}},
    fun1_4        =>{exittoken =>{default=>'ARG'},
                     nextstate =>{s      =>'var1_1orfun1_1'}}
};

bless($dfa,"DFA");

sub lex {
    my $self = shift;
    my @input = split('',shift);
    my @output = ();
    my $buffer = '';
    my $currentstate = $self->{start};
    for my $c (@input) {
        #exit action
        if( my $a = $currentstate->{exittoken} ) {
            if( my $tt = defined($a->{$c})?$a->{$c}:$a->{default} ) {
                push(@output,{type=>$tt,value=>$buffer});
                $buffer = '';
            }
        }#end exit action if
        #state transition
        my $s = $currentstate->{nextstate}->{$c} || 'start';
        $currentstate = $self->{$s};
        $buffer = $buffer.$c;
        #entry action
        if( my $tt = $currentstate->{entrytoken} ) {
            push(@output,{type=>$tt,value=>$buffer});
            $buffer = '';
        }#end entry action if
    }#end for loop
   #eof exit action
    if($buffer) {
        my $a = $currentstate->{exittoken};
        my $tt = ($a)?$a->{default}:'OTHER';
        push(@output,{type=>$tt,value=>$buffer});
    }
    return @output;
}#end function lex

my $inputstring = 'sin(';
print("an input of $inputstring produced the following output.\n");
for my $tok ($dfa->lex($inputstring)) {
    print("$tok->{type},$tok->{value}\n");
}
$inputstring = 'sisin(si';
print("an input of $inputstring produced the following output.\n");
for my $tok ($dfa->lex($inputstring)) {
    print("$tok->{type},$tok->{value}\n");
}
$inputstring = 'sin(sisin(';
print("an input of $inputstring produced the following output.\n");
for my $tok ($dfa->lex($inputstring)) {
    print("$tok->{type},$tok->{value}\n");
}