113 lines
1.7 KiB
Text
113 lines
1.7 KiB
Text
# Working With Floating Point
|
|
|
|
Some RETRO systems include support for floating point numbers.
|
|
When present, this is built over the system `libm` using the
|
|
C `double` type.
|
|
|
|
Floating point values are typically 64 bit IEEE 754 double
|
|
precision (1 bit for the sign, 11 bits for the exponent, and
|
|
the remaining 52 bits for the value), i.e. 15 decimal digits
|
|
of precision.
|
|
|
|
## Prefix
|
|
|
|
Floating point numbers start with a `.`
|
|
|
|
Examples:
|
|
|
|
Token Value
|
|
.1 1.0
|
|
.0.5 0.5
|
|
.-.4 -0.4
|
|
.1.3 1.3
|
|
|
|
## Namespace
|
|
|
|
Floating point words are in the `f:` namespace. There is also
|
|
a related `e:` namespace for *encoded values*, which allows
|
|
storing of floats in standard memory.
|
|
|
|
## Operation
|
|
|
|
Floating point values exist on a separate stack, and are bigger
|
|
than the standard memory cells, so can not be directly stored
|
|
and fetched from memory.
|
|
|
|
The floating point system also provides an alternate stack that
|
|
can be used to temporarily store values.
|
|
|
|
f:nip
|
|
f:over
|
|
f:pop
|
|
f:adepth
|
|
f:push
|
|
f:dump-astack
|
|
f:dump-stack
|
|
f:depth
|
|
f:drop
|
|
f:drop-pair
|
|
f:dup
|
|
f:dup-pair
|
|
f:tuck
|
|
f:swap
|
|
|
|
|
|
f:*
|
|
f:+
|
|
f:-
|
|
f:-INF
|
|
f:-eq?
|
|
f:-inf?
|
|
f:/
|
|
f:E
|
|
f:E1
|
|
f:INF
|
|
f:NAN
|
|
f:PI
|
|
f:abs
|
|
f:acos
|
|
f:asin
|
|
f:atan
|
|
f:between?
|
|
f:case
|
|
f:ceiling
|
|
f:cos
|
|
f:dec
|
|
f:eq?
|
|
f:fetch
|
|
f:floor
|
|
f:gt?
|
|
f:inc
|
|
f:inf?
|
|
f:limit
|
|
f:log
|
|
f:lt?
|
|
f:max
|
|
f:min
|
|
f:nan?
|
|
f:negate
|
|
f:negative?
|
|
f:positive?
|
|
f:power
|
|
f:put
|
|
f:rot
|
|
f:round
|
|
f:sign
|
|
f:signed-sqrt
|
|
f:signed-square
|
|
f:sin
|
|
f:sqrt
|
|
f:square
|
|
f:store
|
|
f:tan
|
|
f:to-e
|
|
f:to-number
|
|
f:to-string
|
|
f:tuck
|
|
|
|
## Encoded Values
|
|
|
|
RETRO provides a means of encoding and decoding floating point
|
|
values into standard integer cells. This is based on the paper
|
|
"Encoding floating point values to shorter integers" by Kiyoshi
|
|
Yoneda and Charles Childers.
|