BigNumber class

A BigNumber represents an arbitrary-precision signed integer backed by the TomsFastMath (libtfm) C library, supporting numbers up to 4096 bits. A multiplication accepts operands of up to 2048 bits each. The default property is ValueString.

Dim a As New BigNumber
Dim b As New BigNumber
Dim result As New BigNumber

a.ValueString = "123456789012345678901234567890"
b.ValueString = "987654321098765432109876543210"
result.AssignAddition a, b
Debug.Print result.ValueString

Note

This class requires twinBASIC BETA 434 or newer. Overflow errors are not trapped. String-to-value conversions silently stop at the first invalid character — for example, setting ValueHex = "ABC123he" stores &HABC123 without raising an error.

Properties
Methods
Comparison functions
Example
See Also

Properties

ValueString

Returns or sets the value as a decimal string representation. Default property.

Syntax: object.ValueString [ = value ]

value: A String containing a decimal integer, optionally preceded by a minus sign. Conversion stops at the first character that is not a valid decimal digit.

The getter returns the decimal digits, preceded by a minus sign for a negative value.

ValueHex

Returns or sets the value as a hexadecimal string representation.

Syntax: object.ValueHex [ = value ]

value: A String containing a hexadecimal integer (digits 0–9 and A–F, case-insensitive), optionally preceded by a minus sign. Conversion stops at the first character that is not a valid hex digit.

The getter returns upper-case digits without leading zeros, preceded by a minus sign for a negative value.

ValueOctal

Returns or sets the value as an octal string representation.

Syntax: object.ValueOctal [ = value ]

value: A String containing an octal integer (digits 0–7), optionally preceded by a minus sign. Conversion stops at the first character that is not a valid octal digit.

The getter returns the digits without leading zeros, preceded by a minus sign for a negative value.

ValueBinary

Returns or sets the value as a binary string representation.

Syntax: object.ValueBinary [ = value ]

value: A String containing a binary integer (digits 0 and 1), optionally preceded by a minus sign. Conversion stops at the first character that is not 0 or 1.

The getter returns the digits without leading zeros, preceded by a minus sign for a negative value.

IsNegative

Returns or sets whether the value is negative.

Syntax: object.IsNegative [ = value ]

value: A Boolean. Setting True marks the number as negative; setting False marks it as positive.

Methods

AssignAddition

Sets this instance to a + b.

Syntax: object.AssignAddition a, b

a: required A BigNumber holding the first operand.
b: required A BigNumber holding the second operand.

AssignSubtraction

Sets this instance to a - b.

Syntax: object.AssignSubtraction a, b

a: required A BigNumber holding the minuend.
b: required A BigNumber holding the subtrahend.

AssignMultiplication

Sets this instance to a * b.

Syntax: object.AssignMultiplication a, b

a: required A BigNumber holding the first factor.
b: required A BigNumber holding the second factor.

AssignDivision

Sets this instance to the integer quotient a \ b, truncated toward zero. Raises run-time error 5 if b is zero.

Syntax: object.AssignDivision a, b

a: required A BigNumber holding the dividend.
b: required A BigNumber holding the divisor. Must not be zero.

AssignModulus

Sets this instance to a Mod b. The result is zero or has the sign of b, so -7 Mod 2 is 1 and 7 Mod -2 is -1. Raises run-time error 5 if b is zero.

Syntax: object.AssignModulus a, b

a: required A BigNumber holding the dividend.
b: required A BigNumber holding the divisor. Must not be zero.

AssignSquared

Sets this instance to a * a (the square of a).

Syntax: object.AssignSquared a

a: required A BigNumber holding the value to square.

AssignAdditionModulus

Sets this instance to (a + b) Mod mod_c.

Syntax: object.AssignAdditionModulus a, b, mod_c

a: required A BigNumber holding the first addend.
b: required A BigNumber holding the second addend.
mod_c: required A BigNumber holding the modulus.

AssignSubtractionModulus

Sets this instance to (a - b) Mod mod_c.

Syntax: object.AssignSubtractionModulus a, b, mod_c

a: required A BigNumber holding the minuend.
b: required A BigNumber holding the subtrahend.
mod_c: required A BigNumber holding the modulus.

AssignMultiplicationModulus

Sets this instance to (a * b) Mod mod_c.

Syntax: object.AssignMultiplicationModulus a, b, mod_c

a: required A BigNumber holding the first factor.
b: required A BigNumber holding the second factor.
mod_c: required A BigNumber holding the modulus.

AssignSquaredModulus

Sets this instance to (a * a) Mod mod_b.

Syntax: object.AssignSquaredModulus a, mod_b

a: required A BigNumber holding the value to square.
mod_b: required A BigNumber holding the modulus.

AssignModularMultiplicativeInverse

Sets this instance to the modular multiplicative inverse of a modulo mod_b — the value x such that (a * x) Mod mod_b = 1. Raises run-time error 5 if the inverse does not exist.

Syntax: object.AssignModularMultiplicativeInverse a, mod_b

a: required A BigNumber holding the value to invert.
mod_b: required A BigNumber holding the modulus.

AssignGreatestCommonDivisor

Sets this instance to the greatest common divisor of a and b. The signs of a and b are ignored; the result is always non-negative.

Syntax: object.AssignGreatestCommonDivisor a, b

a: required A BigNumber holding the first value.
b: required A BigNumber holding the second value.

AssignLeastCommonMultiple

Sets this instance to the least common multiple of a and b. The signs of a and b are ignored.

Syntax: object.AssignLeastCommonMultiple a, b

a: required A BigNumber holding the first value.
b: required A BigNumber holding the second value.

AssignShiftRight

Sets this instance to a right-shifted by shiftAmount_b bits (equivalent to integer division by 2^shiftAmount_b, truncated toward zero, so shifting -1 right by any positive amount gives 0).

Syntax: object.AssignShiftRight a, shiftAmount_b

a: required A BigNumber holding the value to shift.
shiftAmount_b: required A Long specifying the number of bit positions to shift right.

AssignShiftLeft

Sets this instance to a left-shifted by shiftAmount_b bits (equivalent to multiplication by 2^shiftAmount_b).

Syntax: object.AssignShiftLeft a, shiftAmount_b

a: required A BigNumber holding the value to shift.
shiftAmount_b: required A Long specifying the number of bit positions to shift left.

AssignNegation

Sets this instance to the arithmetic negation of a (-a).

Syntax: object.AssignNegation a

a: required A BigNumber holding the value to negate.

AssignNegation is declared as a Function returning Boolean, but the return value is never set and is always False.

AssignAbsolute

Sets this instance to the absolute value of a.

Syntax: object.AssignAbsolute a

a: required A BigNumber holding the value whose absolute value is taken.

AssignAbsolute is declared as a Function returning Boolean, but the return value is never set and is always False.

AssignFromLong

Sets this instance to a value from a native Long integer.

Syntax: object.AssignFromLong a

a: required A Long holding the value to assign. Negative values (including &H80000000) are handled correctly.

HandleError

Examines the last status code the class stored from the library and raises run-time error 5 if it is a failure. The error description is “invalid operation” or “out of memory”.

Syntax: object.HandleError

The string-conversion properties, AssignDivision, AssignModulus, the four modular-arithmetic methods (AssignAdditionModulus, AssignSubtractionModulus, AssignMultiplicationModulus, AssignSquaredModulus) and AssignModularMultiplicativeInverse store the library’s status and call HandleError themselves. The other methods do not store a status. The stored status stays in place until one of those members runs again, so calling HandleError later raises the error again.

Comparison functions

IsEqualTo

Returns True if this instance equals b.

Syntax: object.IsEqualTo( b )

b: required A BigNumber to compare against.

IsLessThan

Returns True if this instance is less than b.

Syntax: object.IsLessThan( b )

b: required A BigNumber to compare against.

IsLessThanOrEqualTo

Returns True if this instance is less than or equal to b.

Syntax: object.IsLessThanOrEqualTo( b )

b: required A BigNumber to compare against.

IsGreaterThan

Returns True if this instance is greater than b.

Syntax: object.IsGreaterThan( b )

b: required A BigNumber to compare against.

IsGreaterThanOrEqualTo

Returns True if this instance is greater than or equal to b.

Syntax: object.IsGreaterThanOrEqualTo( b )

b: required A BigNumber to compare against.

Example

This example computes the factorial of 50 using BigNumber arithmetic.

Public Function Factorial50() As String
    Dim result As New BigNumber
    Dim factor As New BigNumber
    Dim temp As New BigNumber

    result.AssignFromLong 1

    Dim i As Long
    For i = 2 To 50
        factor.AssignFromLong i
        temp.AssignMultiplication result, factor
        result.ValueString = temp.ValueString   ' copy temp into result
    Next i

    Factorial50 = result.ValueString
End Function