float16
Arduino library to implement float16 data type.
Description
This experimental library defines the float16 (2 byte) data type, including conversion function to and from float32 type. It is definitely work in progress.
The library implements the Printable interface so one can directly print the float16 values in any stream e.g. Serial.
The primary usage of the float16 data type is to efficiently store and transport a floating point number. As it is only 2 bytes where float and double have typical 4 and 8, gains can be made at the price of range and precision.
Specifications
| attribute | value | notes |
|---|---|---|
| Size | 2 bytes | |
| sign | 1 bit | |
| mantissa | 11 bit | ~ 3 digits |
| exponent | 4 bit | |
| minimum | 1.0009765625 | 1 + 2^−10 |
| maximum | 65504 | |
Interface
to elaborate
Constructors
- float16(void) defaults to zero.
- float16(double f) constructor.
- float16(const float16 &f) copy constructor.
Conversion
- double toDouble(void) convert to double (or float)
- size_t printTo(Print& p) const Printable interface.
- void setDecimals(uint8_t d) idem, used for printTo.
- uint8_t getDecimals() idem.
Note the setDecimals takes one byte per object which is not efficient for arrays. See array example for efficient storage using set/getBinary() functions.
Compare
to elaborate
Notes
comparison functions
First version of inequality operations are implemented by converting data to double and compare those. The strategy is to get these working first and optionally optimize them later.
TODO (future)
to get focus on getting things done...
0.1.4
the following should work:
- update documentation
- positive numbers
- negative numbers
- infinity
- rounding to zero (e.g. 1e-30)
- array of numbers.
- unit tests of the above..
0.1.5
- update documentation
- comparison operators
- unit tests of the above..
0.1.6
- update documentation
- get basic math working (+-*/)
- isNan()
- isINF()
- abs()
- sgn()
- unit tests of the above..
later
- update documentation
- get basic math II working += -= *= /=
- divide by zero errors.
- f16tof32() + f32tof16()
- rewrite toDouble with bit magic
- ...