use strict;
use warnings;
use feature "say";
use constant DEBUG => 1;

my $epsilon = 1e-12; # precision
my ($result, $step) = (0, 10); # arbitrary start values
my $equation = "(2*(4*x-8)+3*x)-(10*x+1-9)"; # " = 0" omitted
$equation =~ s/x/\$x/g;
my $eval = create_eval($equation); # currying the equation for simplicity

my $debug = 1;
while (1) {
	my $val = $eval->($result);
	last if abs $val < $epsilon;
	my $new_result = $result + $step;
	my $temp = $eval->($new_result);
	say "x = $result ; val = $val ; temp = $temp; step = $step" if DEBUG;
	$result = $new_result and last if abs $temp < $epsilon;
	if ($temp == $val) {
		say "No solution for this equation";
		undef $result;
		last;
	 }
	if (($val > 0 and $temp < 0) or ($val < 0 and $temp > 0)) {
		while (1) {
			$step = 0;
			my $avg = ($result + $new_result) /2;
			my $avg_val = $eval->($avg);
			# say "x = $result; val = $val ; temp = $temp; step = $step; avg = $avg" if DEBUG;
			printf "%s%.15f%s%.15f%s%.15f%s%.15f\n", "x = ", $result, " val = ", $val, " temp = ", $temp, " avg = ", $avg;
			$new_result = $avg and last if abs $avg_val < $epsilon;
			if ($avg_val > 0) {
				$result = $avg and $val= $avg_val if $val > 0;
				$new_result = $avg and $temp = $avg_val if $temp > 0;
			} else {
				$result = $avg and $val = $avg_val if $val < 0;
				$new_result = $avg and $temp = $avg_val if $temp < 0;
			}
		}
	}						
	$step = -$step and next if $temp < $val and $val < 0;
	$step /= 2 and next if abs $temp > abs $val;      # we are further from 0, reduce step by half
	$result =$new_result;      # $temp is closer to 0, let's continue with $new_resultp
	
}

printf "%s%.10f\n", "Result is: ", $result;# if defined $result;

sub create_eval {
	my $formula = shift;
	return sub { my $x = shift; return eval($formula);}
}