This Julia module gives an alternative to `Complex`

numbers and their
operations to give mathematically more sensible results.

Standard complex field operations in Julia work fine; the problems
begin to arise when dividing by zero. It is logical to extend the real
numbers with a positive infinity and a negative infinity. And we have
both `+Inf`

and `-Inf`

in Julia. However, there are problems with the
implementation of infinite values for Julia `Complex`

numbers. Here
are some examples.

```
# For real numbers, division by 0 gives an infinite result
julia> 1/0
Inf
# This division by 0 for complex numbers is fine
julia> (2+3im)/0
Inf + Inf*im
# But this one doesn't make sense
julia> 2im/0
NaN + Inf*im
# For real numbers we have the following sensible result
julia> (Inf + 3) == (Inf + 2)
true
# But it breaks for complex numbers
julia> (Inf + 3im) == (Inf + 2im)
false
```

This module defines an alternative to `Complex`

numbers in which there is a
single infinite value (we call `ComplexInfinity`

). We introduce a new type
called `RC`

(an abbreviation for Riemann Complex number). Let's see how the
previous calculations work in this new context:

```
julia> using RiemannComplexNumbers
julia> (2+3IM)/0
ComplexInf
julia> 2IM/0
ComplexInf
julia> Inf + 3IM == Inf + 2IM
true
```

The constant `IM`

is the replacement for `im`

that can be used to construct
Riemann Complex numbers. In general, wrapping values in `RC`

will work:

```
julia> RC(2)
2 + 0IM
julia> RC(3-im)
3 - 1IM
```

Dividing by zero gives the following:

```
julia> (2-3IM)/0
ComplexInf
julia> 3/0IM
ComplexInf
julia> 0/0IM
ComplexNaN
```

To convert an `RC`

number to a `Complex`

do this:

```
julia> z = 3.5 - 5IM
3.5 - 5.0IM
julia> Complex(z)
3.5 - 5.0im
```

Basic arithmetic operations work exactly the same for `RC`

numbers as for `Complex`

but will be slower (to deal with division by zero and operations with `ComplexInf`

and `ComplexNaN`

).

Some basic functions (such as `sqrt`

and `exp`

) are provided. See the `functions.jl`

file in the `src`

directory.

Some `LinearAlgebra`

operations don't work; I'm not sure why. For example,
evaluating the determinant of an `RC`

matrix throws errors.

01/13/2015

3 months ago

58 commits