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I should go to bed.

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Lokathor 2018-12-16 02:22:07 -07:00
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book/src/02-concepts/02-bios.md
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@ -191,13 +191,13 @@ to invoke. If you're in 16-bit code you use the value directly, and if you're in
The GBA doesn't have hardware division. You have to do it in software.
You can implement that yourself (we might get around to trying that, i was even
sent [a link to a
We could potentially implement this in Rust (we might get around to trying that,
I was even sent [a link to a
paper](https://www.microsoft.com/en-us/research/wp-content/uploads/2008/08/tr-2008-141.pdf)
that I promptly did not read), or you can call the BIOS to do it for you and
trust that it's being as efficient as possible.
that I promptly did not actually read right away), or you can call the BIOS to
do it for you and trust that big N did a good enough job.
GBATEK gives a very clear explanation of it:
GBATEK gives a fairly clear explanation of our inputs and outputs:
```txt
Signed Division, r0/r1.
@ -211,11 +211,11 @@ For example, incoming -1234, 10 should return -123, -4, +123.
The function usually gets caught in an endless loop upon division by zero.
```
Of course, the math folks tell me that the `r1` value should be properly called
the "remainder" not the "modulus". We'll go with that for our function, doesn't
hurt to use the correct names. The function itself is a single assert, then we
name some bindings without giving them a value, make the asm call, and then
return what we got.
The math folks tell me that the `r1` value should be properly called the
"remainder" not the "modulus". We'll go with that for our function, doesn't hurt
to use the correct names. The function itself is an assert against dividing by
`0`, then we name some bindings _without_ giving them a value, we make the asm
call, and then return what we got.
```rust
pub fn div_rem(numerator: i32, denominator: i32) -> (i32, i32) {