Function predecessor

predecessor(c: number): number
Returns the largest representable ChordAngle less than this one.

Note the following special cases:
```
InfChordAngle.Predecessor == StraightChordAngle
ChordAngle(0).Predecessor == NegativeChordAngle
NegativeChordAngle.Predecessor == NegativeChordAngle
```
Parameters
- c: number
Returns number
- Defined in work/s2js/s2js/s1/chordangle.ts:165