# BigRatInterval

* © 2018 John Abbott, Anna M. Bigatti*

GNU Free Documentation License, Version 1.2

CoCoALib Documentation Index
## Examples

## User documentation

`BigRatInterval`

is designed to represent (finite, non-empty) intervals
with rational end points.

### Constructors and pseudo-constructors

`BigRatInterval(lwb, upb)`

creates an interval with lower end point `lwb`

and upper end point `upb`

; gives error if `lwb > upb`

### Queries and views

Let `I`

be a `BigRatInterval`

`min(I)`

-- gives the lower end point of `I`

`max(I)`

-- gives the upper end point of `I`

`width(I)`

-- gives the width of `I`

as a `BigRat`

`IsZeroInside(I)`

-- true iff `min(I) < 0 and max(I) > 0`

### Operations

Basic interval arithmetic operations between two intervals `I1`

and `I2`

:

`I1 + I2`

`I1 - I2`

`I1 * I2`

`I1 / I2`

gives error if `I2`

contains 0
`merge(I1, I2)`

union, but error if `I1`

and `I2`

are disjoint.
`square(I1)`

like `I1*I1`

but ensures lower bound is non-negative.
`soften(I1)`

widen `I1`

to make its end points nicer numbers (PROTOTYPE!)

Basic arithmetic operations between an interval `I`

and a rational `q`

:

`I + q`

and `q + I`

`I - q`

and `q - I`

`I * q`

and `q * I`

Division is not yet supported!

## Maintainer documentation

I have preferred simplicity over efficiency for this first version.

## Bugs, shortcomings and other ideas

Not efficient!

What should the interface to `soften`

be? Is there a better fn name?

## Main changes

**2018**

- April (v0.99563): first release