gbdev/rgbds
1
0
Fork 0
mirror of https://github.com/gbdev/rgbds.git synced 2025-11-26 21:12:07 +00:00
Code Issues Packages Projects Releases Wiki Activity

Implement opt Q for fixed-point precision, and q literals (e.g. 12.34q8) (#958)

Browse Source 
Fixes #957

Co-authored-by: ISSOtm <eldredhabert0@gmail.com>
This commit is contained in:
Rangi
2022-09-04 18:47:32 -04:00
committed by GitHub
parent 889302a9e2
commit 98a6dffbca
20 changed files with 253 additions and 56 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
man/rgbasm.5
View File

@@ -208,13 +208,14 @@ section.
The instructions in the macro-language generally require constant expressions.
.Ss Numeric formats
There are a number of numeric formats.
.Bl -column -offset indent "Fixed point (Q16.16)" "Prefix"
.Bl -column -offset indent "Precise fixed-point" "Prefix"
.It Sy Format type Ta Sy Prefix Ta Sy Accepted characters
.It Hexadecimal Ta $ Ta 0123456789ABCDEF
.It Decimal Ta none Ta 0123456789
.It Octal Ta & Ta 01234567
.It Binary Ta % Ta 01
.It Fixed point (Q16.16) Ta none Ta 01234.56789
.It Fixed-point Ta none Ta 01234.56789
.It Precise fixed-point Ta none Ta 12.34q8
.It Character constant Ta none Ta \(dqABYZ\(dq
.It Gameboy graphics Ta \` Ta 0123
.El
@@ -301,9 +302,19 @@ and
.Ic \&!
returns 1 if the operand was 0, and 0 otherwise.
.Ss Fixed-point expressions
Fixed-point numbers are basically normal (32-bit) integers, which count 65536ths instead of entire units, offering better precision than integers but limiting the range of values.
The upper 16 bits are used for the integer part and the lower 16 bits are used for the fraction (65536ths).
Since they are still akin to integers, you can use them in normal integer expressions, and some integer operators like
Fixed-point numbers are basically normal (32-bit) integers, which count fractions instead of whole numbers.
They offer better precision than integers but limit the range of values.
By default, the upper 16 bits are used for the integer part and the lower 16 bits are used for the fraction (65536ths).
The default number of fractional bits can be changed with the
.Fl Q
command-line option.
You can also specify a precise fixed-point value by appending a
.Dq q
to it followed by the number of fractional bits, such as
.Ql 12.34q8 .
.Pp
Since fixed-point values are still just integers, you can use them in normal integer expressions.
Some integer operators like
.Sq +
and
.Sq -
@@ -317,9 +328,9 @@ delim $$
.EN
.Bl -column -offset indent "ATAN2(x, y)"
.It Sy Name Ta Sy Operation
.It Fn DIV x y Ta $x \[di] y$
.It Fn MUL x y Ta $x \[mu] y$
.It Fn FMOD x y Ta $x % y$
.It Fn DIV x y Ta Fixed-point division $( x \[di] y ) \[mu] ( 2 ^ precision )$
.It Fn MUL x y Ta Fixed-point multiplication $( x \[mu] y ) \[di] ( 2 ^ precision )$
.It Fn FMOD x y Ta Fixed-point modulo $( x % y ) \[di] ( 2 ^ precision )$
.It Fn POW x y Ta $x$ to the $y$ power
.It Fn LOG x y Ta Logarithm of $x$ to the base $y$
.It Fn ROUND x Ta Round $x$ to the nearest integer
@@ -2034,7 +2045,7 @@ POPO
The options that
.Ic OPT
can modify are currently:
.Cm b , g , p , r , h , L ,
.Cm b , g , p , Q , r , h , L ,
and
.Cm W .
The Boolean flag options