Math::BigInt - Revision history

129.6.61.113 at 19:11, 2 June 2005

2005-06-02T19:11:29Z

129.6.61.113: /* Methods Work In-Place */

2005-06-02T19:05:27Z

Methods Work In-Place

129.6.61.113: /* Methods Work In-Place */

2005-06-02T19:05:21Z

Methods Work In-Place

209.77.48.14: /* Use */

2005-04-17T07:07:39Z

Use

209.77.48.14: /* Methods Work In-Place */

2005-04-17T07:07:16Z

Methods Work In-Place

161.253.9.181: /* In-place Modification */

2005-04-08T20:50:01Z

In-place Modification

161.253.9.181: /* Use */

2005-04-08T19:05:28Z

Use

161.253.9.181: /* Converting a binary string to a BigInt */

2005-04-08T18:28:49Z

Converting a binary string to a BigInt

161.253.9.181: /* Converting a binary string to a BigInt */

2005-04-03T16:23:33Z

Converting a binary string to a BigInt

161.253.9.181: /* Converting a binary string to a BigInt */

2005-04-02T18:17:41Z

Converting a binary string to a BigInt

← Older revision	Revision as of 19:11, 2 June 2005
Line 1:	Line 1:
	+	=In-place vs. Copy Modification=

	+	Whether Math::BigInt does its thing in-place or not depends on whether you use the methods or the overloaded operators.
	+
	+	==Methods Work In-Place==
	+
	+	If you use the methods, modification is in-place, regardless of context. A new object is not created for a result.
	+
	+	<nowiki>
	+	use Math::BigInt;
	+
	+	# This reblessing isn't fail-safe
	+	# but it works for this example
	+	sub same_object ($$) {
	+	my $pa = ref($_[0]) or return undef;
	+	my $pb = ref($_[1]) or return undef;
	+	my $v;
	+	bless $_[0], 'Xana::Fake';
	+	bless $_[1], 'Xana::Fake';
	+	$v = $_[0] == $_[1];
	+	bless $_[1], $pb;
	+	bless $_[0], $pa;
	+	$v;
	+	}
	+
	+	# Void context
	+	my $a = new Math::BigInt '27';
	+
	+	$a->badd(3);
	+	$a == '30'
	+	or die "a=$a";
	+
	+	# Scalar context
	+	my $b = new Math::BigInt '27';
	+	my $c = $b->badd(3);
	+	$b == '30'
	+	or die "b=$b";
	+	same_object($b,$c)
	+	or die "b and c are not the same object";
	+	</nowiki>
	+
	+	==Overloads Use Copies==
	+
	+	Meanwhile, overloaded operators treat the objects like regular scalars; nothing is modified in place unless an assignment operator (including <code>+=</code>, <code>*=</code>, ''etc.'', but not <code>=</code> for Perl reasons) is used.
	+
	+	# Void context using overloads
	+	# does not work in-place
	+	my $d = new Math::BigInt '57';
	+	$d + 3;
	+	$d == '57'
	+	or die "d=$d";
	+
	+	# Scalar context using overloads
	+	# does not work in-place
	+	my $e = new Math::BigInt '97';
	+	my $f = $e + 4;
	+	$e == '97'
	+	or die "e=$e";
	+	$f == '101'
	+	or die "f=$f";
	+
	+	=Converting a binary string to a BigInt=
	+
	+	This code conveniently reinterprets raw bytes as [[hexadecimals\|hexadecimal]] digits, big-endian style, so that the data may be cast into a bigint. This code doesn't do any buffering; for that, try my new Xana::Math::RawDataUtil module in [[Xana]].
	+
	+	# Unsigned
	+	my $a = "ZYXWVUT";
	+	my $ba = new Math::BigInt '0x' . unpack('H*',$a);
	+	# Test
	+	$ba == '25430983861228884'
	+	or die "ba=$ba";
	+
	+	# Signed
	+	sub raw_to_signed_bigint ($) {
	+	# The MSB is the sign bit.
	+	if(unpack('C',substr($_[0],0,1)) & 0x80) {
	+	my $hex = unpack('H*',$_[0]);
	+	# Invert the hex digits.
	+	$hex =~ tr/0123456789aAbBcCdDeEfF/fedcba9876554433221100/;
	+	my $bigint = new Math::BigInt "0x$hex";
	+	# Then, the ones complement is the right answer.
	+	return $bigint->bnot();
	+	} else {
	+	# The normal unsigned thing.
	+	return Math::BigInt->new( '0x' . unpack('H*',$_[0]) );
	+	}
	+	}
	+
	+	# Tests
	+	my $bb = raw_to_signed_bigint "\xFF\x54\xAB\x56\x73\x14\xE0\xF5\x2E";
	+	$bb == '-12345678901234567890'
	+	or die "bb=$bb";
	+
	+	my $bc = raw_to_signed_bigint "\xFF";
	+	$bc == '-1'
	+	or die "bc=$bc";
	+
	+	my $bd = raw_to_signed_bigint "ZYXWVUT";
	+	$bd == '25430983861228884'
	+	or die "bd=$bd";
	+
	+	=See Also=
	+
	+	* [http://search.cpan.org/~tels/Math-BigInt-1.75/lib/Math/BigInt.pm CPAN]

← Older revision		Revision as of 19:05, 2 June 2005
Line 1:		Line 1:

−
−	~~=In-place vs. Copy Modification=~~
−
−	~~Whether Math::BigInt does its thing in-place or not depends on whether you use the methods or the overloaded operators.~~
−
−	~~==Methods Work In-Place==~~
−
−	~~If you use the methods, modification is in-place, regardless of context. A new object is not created for a result.~~
−
−	~~<nowiki>~~
−	~~use Math::BigInt;~~
−
−	~~# Apparently part of this program got lost.~~
−	~~# Will try to find it later. -- PSM~~
−
−	~~bless $_[1], $pb;~~
−	~~bless $_[0], $pa;~~
−	~~$v;~~
−	}
−
−	~~# Void context~~
−	~~my $a = new Math::BigInt '27';~~
−
−	~~$a->badd(3);~~
−	~~$a == '30'~~
−	~~or die "a=$a";~~
−
−	~~# Scalar context~~
−	~~my $b = new Math::BigInt '27';~~
−	~~my $c = $b->badd(3);~~
−	~~$b == '30'~~
−	~~or die "b=$b";~~
−	~~same_object($b,$c)~~
−	~~or die "b and c are not the same object";~~
−	~~</nowiki>~~
−
−	~~==Overloads Use Copies==~~
−
−	Meanwhile, overloaded operators treat the objects like regular scalars; nothing is modified in place unless an assignment operator (including <code>+=</code>, <code>*=</code>, ''etc.'', but not <code>=</code> for Perl reasons) is used.
−
−	~~# Void context using overloads~~
−	~~# does not work in-place~~
−	~~my $d = new Math::BigInt '57';~~
−	~~$d + 3;~~
−	~~$d == '57'~~
−	~~or die "d=$d";~~
−
−	~~# Scalar context using overloads~~
−	~~# does not work in-place~~
−	~~my $e = new Math::BigInt '97';~~
−	~~my $f = $e + 4;~~
−	~~$e == '97'~~
−	~~or die "e=$e";~~
−	~~$f == '101'~~
−	~~or die "f=$f";~~
−
−	~~=Converting a binary string to a BigInt=~~
−
−	This code conveniently reinterprets raw bytes as [[hexadecimals\|hexadecimal]] digits, big-endian style, so that the data may be cast into a bigint. This code doesn't do any buffering; for that, try my new Xana::Math::RawDataUtil module in [[Xana]].
−
−	~~# Unsigned~~
−	~~my $a = "ZYXWVUT";~~
−	~~my $ba = new Math::BigInt '0x' . unpack('H*',$a);~~
−	~~# Test~~
−	~~$ba == '25430983861228884'~~
−	~~or die "ba=$ba";~~
−
−	~~# Signed~~
−	~~sub raw_to_signed_bigint ($) {~~
−	~~# The MSB is the sign bit.~~
−	~~if(unpack('C',substr($_[0],0,1)) & 0x80) {~~
−	~~my $hex = unpack('H*',$_[0]);~~
−	~~# Invert the hex digits.~~
−	~~$hex =~ tr/0123456789aAbBcCdDeEfF/fedcba9876554433221100/;~~
−	~~my $bigint = new Math::BigInt "0x$hex";~~
−	~~# Then, the ones complement is the right answer.~~
−	~~return $bigint->bnot();~~
−	~~} else {~~
−	~~# The normal unsigned thing.~~
−	~~return Math::BigInt->new( '0x' . unpack('H*',$_[0]) );~~
−	}
−	}
−
−	~~# Tests~~
−	~~my $bb = raw_to_signed_bigint "\xFF\x54\xAB\x56\x73\x14\xE0\xF5\x2E";~~
−	~~$bb == '-12345678901234567890'~~
−	~~or die "bb=$bb";~~
−
−	~~my $bc = raw_to_signed_bigint "\xFF";~~
−	~~$bc == '-1'~~
−	~~or die "bc=$bc";~~
−
−	~~my $bd = raw_to_signed_bigint "ZYXWVUT";~~
−	~~$bd == '25430983861228884'~~
−	~~or die "bd=$bd";~~
−
−	~~=See Also=~~
−
−	* [http://search.cpan.org/~tels/Math-BigInt-1.75/lib/Math/BigInt.pm CPAN]

@@ Line 9: / Line 9: @@
 If you use the methods, modification is in-place, regardless of context.  A new object is not created for a result.
   use Math::BigInt;
       bless $_[1], $pb;
       bless $_[0], $pa;
@@ Line 18: / Line 22: @@
   # Void context
   my $a = new Math::BigInt '27';
-−
   $a->badd(3);
   $a == '30'
@@ Line 30: / Line 34: @@
   same_object($b,$c)
       or die "b and c are not the same object";
 ==Overloads Use Copies==

← Older revision		Revision as of 07:07, 17 April 2005
Line 1:		Line 1:
−	~~=Use=~~

−	~~Specifying <code>lib</code> forces a library, but if that library isn't installed, fallback is automatic.~~
−
−	~~use Math::BigInt lib => 'Pari,GMP,BitVect';~~

	=In-place vs. Copy Modification=		=In-place vs. Copy Modification=

@@ Line 15: / Line 15: @@
   use Math::BigInt;
       bless $_[1], $pb;
       bless $_[0], $pa;
@@ Line 31: / Line 22: @@
   # Void context
   my $a = new Math::BigInt '27';
   $a->badd(3);
   $a == '30'

@@ Line 5: / Line 5: @@
   use Math::BigInt lib => 'Pari,GMP,BitVect';
-=In-place Modification=
+=In-place vs. Copy Modification=
-Modification is in-place, regardless of context.  A new object is not created for a result.
+Whether Math::BigInt does its thing in-place or not depends on whether you use the methods or the overloaded operators.
   use Math::BigInt;
   # Void context
   my $a = new Math::BigInt '27';
   $a->badd(3);
+  $a == '30'
- print "$a"; # 30
+     or die "a=$a";
   # Scalar context
   my $b = new Math::BigInt '27';
   my $c = $b->badd(3);
-  print "$b"; # 30
+  # Scalar context using overloads
-  print "$c"; # 30
+ # does not work in-place
-  print $b == $c ? "Same object" : "Not same object";
+ my $e = new Math::BigInt '97';
-   # Same object
+ my $f = $e + 4;
 =Converting a binary string to a BigInt=

@@ Line 3: / Line 3: @@
 Specifying <code>lib</code> forces a library, but if that library isn't installed, fallback is automatic.
-  use Math::BigInt lib => 'GMP';
+  use Math::BigInt lib => 'Pari,GMP,BitVect';
 =In-place Modification=

@@ Line 30: / Line 30: @@
 =Converting a binary string to a BigInt=
-Actually, I've implemented something much cooler that exploits Math::BigInt's ability to parse hex strings.  The updated code is part of the new [[Xana]] library Xana::Math::RawDataUtil.
+This code conveniently reinterprets raw bytes as [[hexadecimals|hexadecimal]] digits, big-endian style, so that the data may be cast into a bigint.  This code doesn't do any buffering; for that, try my new Xana::Math::RawDataUtil module in [[Xana]].
-  use Math::BigInt lib => 'GMP';
+ # Unsigned
+ my $a = "ZYXWVUT";
-  # This function works by decoding a binary string
+ my $ba = new Math::BigInt '0x' . unpack('H*',$a);
-  # 3 bytes at a time (4 could cause sign trouble).
+ # Test
-  # Anything that comes from this function is unsigned.
+ $ba == '25430983861228884'
-  sub bin2ubig {
+     or die "ba=$ba";
-    if($len == 0) {
+ # Signed
-      return $cml;
+ sub raw_to_signed_bigint ($) {
+     # The MSB is the sign bit.
-    my $sub;
+ # Tests
-    # The first get is the length % 3.
+ my $bc = raw_to_signed_bigint "\xFF";
-    # This way, the rest of the gets
+ $bc == '-1'
-    # can just be 3.
+     or die "bc=$bc";
-      # But if the length is a multiple of three,
+  my $bd = raw_to_signed_bigint "ZYXWVUT";
-      # cut to the main part.
+  $bd == '25430983861228884'
-      last unless $get;
+     or die "bd=$bd";
 =See Also=
 * [http://search.cpan.org/~tels/Math-BigInt-1.75/lib/Math/BigInt.pm CPAN]

← Older revision		Revision as of 16:23, 3 April 2005
Line 29:		Line 29:

	=Converting a binary string to a BigInt=		=Converting a binary string to a BigInt=
		+
		+	Actually, I've implemented something much cooler that exploits Math::BigInt's ability to parse hex strings. The updated code is part of the new [[Xana]] library Xana::Math::RawDataUtil.

	use Math::BigInt lib => 'GMP';		use Math::BigInt lib => 'GMP';