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diff --git a/lib/MDK/Common/Math.pm b/lib/MDK/Common/Math.pm
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+package MDK::Common::Math;
+
+=head1 NAME
+
+MDK::Common::Math - miscellaneous math functions
+
+=head1 SYNOPSIS
+
+    use MDK::Common::Math qw(:all);
+
+=head1 EXPORTS
+
+=over
+
+=item $PI
+
+the well-known constant 
+
+=item even(INT)
+
+=item odd(INT)
+
+is the number even or odd?
+
+=item sqr(FLOAT)
+
+C<sqr(3)> gives C<9>
+
+=item sign(FLOAT)
+
+returns a value in { -1, 0, 1 }
+
+=item round(FLOAT)
+
+C<round(1.2)> gives C<1>, C<round(1.6)> gives C<2>
+
+=item round_up(FLOAT, INT)
+
+returns the number rounded up to the modulo:
+C<round_up(11,10)> gives C<20>
+
+=item round_down(FLOAT, INT)
+
+returns the number rounded down to the modulo:
+C<round_down(11,10)> gives C<10>
+
+=item divide(INT, INT)
+
+integer division (which is lacking in perl). In array context, also returns the remainder:
+C<($a, $b) = divide(10,3)> gives C<$a is 3> and C<$b is 1>
+
+=item min(LIST)
+
+=item max(LIST)
+
+returns the minimum/maximum number in the list
+
+=item or_(LIST)
+
+is there a true value in the list?
+
+=item and_(LIST)
+
+are all values true in the list?
+
+=item sum(LIST)
+
+=item product(LIST)
+
+returns the sum/product of all the element in the list
+
+=item factorial(INT)
+
+C<factorial(4)> gives C<24> (4*3*2)
+
+=back
+
+=head1 OTHER
+
+the following functions are provided, but not exported:
+
+=over
+
+=item factorize(INT)
+
+C<factorize(40)> gives C<([2,3], [5,1])> as S<40 = 2^3 + 5^1>
+
+=item decimal2fraction(FLOAT)
+
+C<decimal2fraction(1.3333333333)> gives C<(4, 3)> 
+($PRECISION is used to decide which precision to use)
+
+=item poly2(a,b,c)
+
+Solves the a*x2+b*x+c=0 polynomial:
+C<poly2(1,0,-1)> gives C<(1, -1)>
+
+=item permutations(n,p)
+
+A(n,p)
+
+=item combinaisons(n,p)
+
+C(n,p)
+
+=back
+
+=head1 SEE ALSO
+
+L<MDK::Common>
+
+=cut
+
+
+use Exporter;
+our @ISA = qw(Exporter);
+our @EXPORT_OK = qw($PI even odd sqr sign round round_up round_down divide min max or_ and_ sum product factorial);
+our %EXPORT_TAGS = (all => [ @EXPORT_OK ]);
+
+
+our $PRECISION = 10;
+our $PI = 3.1415926535897932384626433832795028841972;
+
+sub even { $_[0] % 2 == 0 }
+sub odd  { $_[0] % 2 == 1 }
+sub sqr  { $_[0] * $_[0] }
+sub sign { $_[0] <=> 0 }
+sub round { int($_[0] + 0.5) }
+sub round_up { my ($i, $r) = @_; $i = int $i; $i += $r - ($i + $r - 1) % $r - 1 }
+sub round_down { my ($i, $r) = @_; $i = int $i; $i -= $i % $r }
+sub divide { my $d = int $_[0] / $_[1]; wantarray() ? ($d, $_[0] % $_[1]) : $d }
+sub min  { my $n = shift; $_ < $n and $n = $_ foreach @_; $n }
+sub max  { my $n = shift; $_ > $n and $n = $_ foreach @_; $n }
+sub or_  { my $n = 0; $n ||= $_ foreach @_; $n }
+sub and_ { my $n = 1; $n &&= $_ foreach @_; $n }
+sub sum  { my $n = 0; $n  += $_ foreach @_; $n }
+sub product { my $n = 1; $n  *= $_ foreach @_; $n }
+
+
+sub factorize {
+    my ($n) = @_;
+    my @r;
+
+    $n == 1 and return [ 1, 1 ];
+    for (my $k = 2; sqr($k) <= $n; $k++) {
+	my $i = 0;
+	for ($i = 0; $n % $k == 0; $i++) { $n /= $k }
+	$i and push @r, [ $k, $i ];
+    }
+    $n > 1 and push @r, [ $n, 1 ];
+    @r;
+}
+
+sub decimal2fraction { # ex: 1.33333333 -> (4, 3)
+    my $n0 = shift;
+    my $precision = 10 ** -(shift || $PRECISION);
+    my ($a, $b) = (int $n0, 1);
+    my ($c, $d) = (1, 0);
+    my $n = $n0 - int $n0;
+    my $k;
+    until (abs($n0 - $a / $c) < $precision) {
+	$n = 1 / $n;
+	$k = int $n;
+	($a, $b) = ($a * $k + $b, $a);
+	($c, $d) = ($c * $k + $d, $c);
+	$n -= $k;
+    }
+    ($a, $c);
+}
+
+sub poly2 {
+    my ($a, $b, $c) = @_;
+    my $d = ($b**2 - 4 * $a * $c) ** 0.5;  
+    (-$b + $d) / 2 / $a, (-$b - $d) / 2 / $a;
+}
+
+# A(n,p)
+sub permutations {
+    my ($n, $p) = @_;
+    my ($r, $i);
+    for ($r = 1, $i = 0; $i < $p; $i++) {
+	$r *= $n - $i;
+    }
+    $r;
+}
+
+# C(n,p)
+sub combinaisons {
+    my ($n, $p) = @_;
+
+    permutations($n, $p) / factorial($p);
+}
+
+sub factorial { permutations($_[0], $_[0]) }
+
+
+1;