package Math::BigPositiveOkayPrecision;

use overload
    '+' =>  \&add,
    #'-' =>  \&sub,
    '*' =>  \&mul,
    '/' =>  \&div,
    '**' => \&pow,
    '^' =>  \&prd,  # $x^$y = factorial($y)/factorial($x)
    '<<' => \&shl,
    '>>' => \&shr,
    '<=>'=> \&cmp,
    '!' =>  \&fct,  # !$x = factorial($x)
    '0+' => \&num,
    '""' => \&str,
    #'neg'=> \&neg,
;

sub new
{
    my $us= shift @_;
    if(  ! @_  ) {
        die "new() needs an object or a value"
            if  ! ref $us;
        return bless \( 0+$$us );
    }
    my $val= shift @_;
    die "Non-positive values not supported yet ($val)"
        if  $val <= 0;
    return bless \log( $val );
}
*Okay::new= \&new;  # Until we get a better module name

sub mul
{
    my( $x, $y )= @_;
    $y= $x->new( $y )
        if  ! ref $y;
    return bless \( $$x + $$y );
}

sub div
{
    my( $x, $y, $rev )= @_;
    $y= $x->new( $y )
        if  ! ref $y;
    ( $x, $y )= ( $y, $x )
        if  $rev;
    return bless \( $$x - $$y );
}

sub pow
{
    my( $x, $y, $rev )= @_;
    $y= $x->new( $y )
        if  ! ref $y;
    ( $x, $y )= ( $y, $x )
        if  $rev;
    return bless \( $$x * exp($$y) );
}

sub add
{
    my( $x, $y )= @_;
    $y= $x->new( $y )
        if  ! ref $y;
    ( $x, $y )= ( $y, $x )
        if  $$y < $$x;
    return bless \( $$y + log( 1 + exp( $$x - $$y ) ) );
}

sub shl
{
    my( $x, $y, $rev )= @_;
    $y= $x->new( $y )
        if  ! ref $y;
    ( $x, $y )= ( $y, $x )
        if  $rev;
    return bless \( $$x + exp($$y)*log(2) );
}

sub shr
{
    my( $x, $y, $rev )= @_;
    $y= $x->new( $y )
        if  ! ref $y;
    ( $x, $y )= ( $y, $x )
        if  $rev;
    return bless \( $$x - exp($$y)*log(2) );
}

sub cmp
{
    my( $x, $y, $rev )= @_;
    $y= $x->new( $y )
        if  ! ref $y;
    ( $x, $y )= ( $y, $x )
        if  $rev;
    return $$x <=> $$y;
}

sub prd
{
    my( $x, $y, $rev )= @_;
    $y= $x->new( $y )
        if  ! ref $y;
    ( $x, $y )= ( $y, $x )
        if  $rev;
    return bless \0
        if  $$y < $$x;
    my $p= $x->new();
    my $m= $x + 1;
    while(  $m <= $y  ) {
        $p= $p * $m;
        $m= $m + 1;
    }
    return $p;
}

sub fct
{
    my( $x )= @_;
    return 1^$x;
}

sub num
{
    my( $x )= @_;
    return exp( $$x );
}

sub str
{
    my( $x )= @_;
    my $exp= int( $$x / log(10) );
    my $mant= exp( $$x - log(10)*$exp );
    $mant= sprintf "%.10f", $mant;
    $mant .=  $exp  ?  "e" . $exp  :  "";
    return $mant
        if  9 < $exp;
    return 0 + $mant;
}

__PACKAGE__;
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