A Rational number is defined as a numerator and a denominator. Both the numerator and the denominator are integers. If you want to match for a rational number, you can do so by matching against this Struct.

Note that directly manipulating the struct, however, is usually a bad idea, as then there are no validity checks, nor wil the rational be simplified.

Use Ratio.new/2 instead.

Returns the absolute version of the given number (which might be an integer, float or Rational).

Examples

iex>Ratio.abs(Ratio.new(-5, 2))
Ratio.new(5, 2)

Adds two rational numbers.

iex> Ratio.add(Ratio.new(1, 4), Ratio.new(2, 4))
Ratio.new(3, 4)

For ease of use, rhs is allowed to be an integer as well:

iex> Ratio.add(Ratio.new(1, 4), 2)
Ratio.new(9, 4)

To perform addition where one of the operands might be another numeric type, use Numbers.add/2 instead, as this will perform the required coercions between the number types:

iex> Ratio.add(Ratio.new(1, 3), Decimal.new("3.14"))
** (FunctionClauseError) no function clause matching in Ratio.add/2

iex> Numbers.add(Ratio.new(1, 3), Decimal.new("3.14"))
Ratio.new(521, 150)

Rounds a number (rational, integer or float) to the largest whole number larger than or equal to num. For negative numbers, this means we are rounding towards negative infinity.

iex> Ratio.ceil(Ratio.new(1, 2)) 1 iex> Ratio.ceil(Ratio.new(5, 4)) 2 iex> Ratio.ceil(Ratio.new(-3, 2)) -1 iex> Ratio.ceil(Ratio.new(400)) 400

Compares two rational numbers, returning :lt, :eg or :gt depending on whether a is less than, equal to or greater than b, respectively.

This function is able to compare rational numbers against integers or floats as well.

This function accepts other types as input as well, comparing them using Erlang's Term Ordering. This is mostly useful if you have a collection that contains other kinds of numbers (builtin integers or floats) as well.

Treats the passed number as a Rational number, and extracts its denominator. For integers, returns 1.

Divides the rational number lhs by the rational number rhs.

iex> Ratio.div(Ratio.new(2, 3), Ratio.new(8, 5))
Ratio.new(5, 12)

For ease of use, allows rhs to be an integer as well as a Ratio struct.

iex> Ratio.div(Ratio.new(2, 3), 10)
Ratio.new(2, 30)

To perform division where one of the operands might be another numeric type, use Numbers.div/2 instead, as this will perform the required coercions between the number types:

iex> Ratio.div(Ratio.new(2, 3), Decimal.new(10))
** (FunctionClauseError) no function clause matching in Ratio.div/2

iex> Numbers.div(Ratio.new(2, 3), Decimal.new(10))
Ratio.new(2, 30)

True if a is equal to b

True if a is equal to b?

Rounds a number (rational, integer or float) to the largest whole number less than or equal to num. For negative numbers, this means we are rounding towards negative infinity.

iex> Ratio.floor(Ratio.new(1, 2)) 0 iex> Ratio.floor(Ratio.new(5, 4)) 1 iex> Ratio.floor(Ratio.new(-3, 2)) -2

True if a is larger than or equal to b

True if a is larger than or equal to b

Check to see whether something is a ratioal struct.

On recent OTP versions that expose :erlang.map_get/2 this function is guard safe.

iex> require Ratio iex> Ratio.is_rational(Ratio.new(1, 2)) true iex> Ratio.is_rational(Ratio.new(10)) true iex> Ratio.is_rational(42) false iex> Ratio.is_rational(%{}) false iex> Ratio.is_rational("My quick brown fox") false

True if a is smaller than b

True if a is smaller than or equal to b

Negates the given rational number.

Examples

iex> Ratio.minus(Ratio.new(5, 3)) Ratio.new(-5, 3)

Multiplies two rational numbers.

iex> Ratio.mult( Ratio.new(1, 3), Ratio.new(1, 2))
Ratio.new(1, 6)

For ease of use, allows rhs to be an integer as well as a Ratio struct.

iex> Ratio.mult( Ratio.new(1, 3), 2)
Ratio.new(2, 3)

To perform multiplication where one of the operands might be another numeric type, use Numbers.mult/2 instead, as this will perform the required coercions between the number types:

iex> Ratio.mult( Ratio.new(1, 3), Decimal.new("3.14"))
** (FunctionClauseError) no function clause matching in Ratio.mult/2

iex> Numbers.mult( Ratio.new(1, 3), Decimal.new("3.14"))
Ratio.new(157, 150)

Creates a new Rational number. This number is simplified to the most basic form automatically.

Rational numbers with a 0 as denominator are not allowed.

Note that it is recommended to use integer numbers for the numerator and the denominator.

Floats

If possible, don't use them.

Using Floats for the numerator or denominator is possible, however, because base-2 floats cannot represent all base-10 fractions properly, the results might be different from what you might expect. See The Perils of Floating Point for more information about this.

Floats are converted into rationals by using Float.ratio (since version 3.0).

Decimals

To use Decimal parameters, the decimal library must be configured in mix.exs.

Examples

iex> Ratio.new(1, 2)
Ratio.new(1, 2)
iex> Ratio.new(100, 300)
Ratio.new(1, 3)
iex> Ratio.new(1.5, 4)
Ratio.new(3, 8)
iex> Ratio.new(Ratio.new(3, 2), 3)
Ratio.new(1, 2)
iex> Ratio.new(Ratio.new(3, 3), 2)
Ratio.new(1, 2)
iex> Ratio.new(Ratio.new(3, 2), Ratio.new(1, 3))
Ratio.new(9, 2)

Converts the passed number as a Rational number, and extracts its denominator. For integers returns the passed number itself.

@spec pow(number() | t(), pos_integer()) :: t()

returns x to the n th power.

x is allowed to be an integer, rational or float (in the last case, this is first converted to a rational).

Will give the answer as a rational number when applicable. Note that the exponent n is only allowed to be an integer.

(so it is not possible to compute roots using this function.)

Examples

iex> Ratio.pow(Ratio.new(2), 4)
Ratio.new(16, 1)
iex> Ratio.pow(Ratio.new(2), -4)
Ratio.new(1, 16)
iex> Ratio.pow(Ratio.new(3, 2), 10)
Ratio.new(59049, 1024)
iex> Ratio.pow(Ratio.new(10), 0)
Ratio.new(1, 1)

Returns the sign of the given number (which might be an integer, float or Rational)

This is:

• 1 if the number is positive.
• -1 if the number is negative.
• 0 if the number is zero.

Subtracts the rational number rhs from the rational number lhs.

iex> Ratio.sub(Ratio.new(1, 4), Ratio.new(2, 4))
Ratio.new(-1, 4)

For ease of use, rhs is allowed to be an integer as well:

iex> Ratio.sub(Ratio.new(1, 4), 2)
Ratio.new(-7, 4)

To perform addition where one of the operands might be another numeric type, use Numbers.sub/2 instead, as this will perform the required coercions between the number types:

iex> Ratio.sub(Ratio.new(1, 3), Decimal.new("3.14"))
** (FunctionClauseError) no function clause matching in Ratio.sub/2

iex> Numbers.sub(Ratio.new(1, 3), Decimal.new("3.14"))
Ratio.new(-421, 150)

@spec to_float(t() | number()) :: float()

Converts the given number to a Float. As floats do not have arbitrary precision, this operation is generally not reversible.

@spec to_float_error(t() | number()) :: {float(), error} when error: t() | number()

Returns a tuple, where the first element is the result of to_float(number) and the second is a conversion error.

The conversion error is calculated by subtracting the original number from the conversion result.

Examples

iex> Ratio.to_float_error(Ratio.new(1, 2))
{0.5, Ratio.new(0, 1)}
iex> Ratio.to_float_error(Ratio.new(2, 3))
{0.6666666666666666, Ratio.new(-1, 27021597764222976)}

Returns a binstring representation of the Rational number. If the denominator is 1 it will still be printed wrapped with Ratio.new.

Examples

iex> Ratio.to_string Ratio.new(10, 7)
"Ratio.new(10, 7)"
iex> Ratio.to_string Ratio.new(10, 2)
"Ratio.new(5, 1)"

@spec trunc(t() | number()) :: integer()

Returns the integer part of number.

Examples

iex> Ratio.trunc(1.7)
1
iex> Ratio.trunc(-1.7)
-1
iex> Ratio.trunc(3)
3
iex> Ratio.trunc(Ratio.new(5, 2))
2