# Absolute value #

This file defines a notational class `Abs`

which adds the unary operator `abs`

and the notation
`|.|`

. The concept of an absolute value occurs in lattice ordered groups and in GL and GM spaces.

Mathematical structures possessing an absolute value often also possess a unique decomposition of
elements into "positive" and "negative" parts which are in some sense "disjoint" (e.g. the Jordan
decomposition of a measure). This file also defines `PosPart`

and `NegPart`

classes
which add unary operators `pos`

and `neg`

, representing the maps taking an element to its positive
and negative part respectively along with the notation `⁺`

and `⁻`

.

## Notations #

The following notation is introduced:

`|.|`

for the absolute value;`.⁺`

for the positive part;`.⁻`

for the negative part.

## Tags #

absolute

Unexpander for the notation `|a|`

for `abs a`

.
Tries to add discretionary parentheses in unparseable cases.