borrow = *elem << (uint::bits - n_bits);
The code above contains a bug that the value of the right operand of the shift operator exceeds the size of the left operand,
because sizeof(*elem) == 32, and 0 <= n_bits < 32 in 64bit architecture.
If `--opt-level` option is not given to rustc, the code above runs as if the right operand is `(uint::bits - n_bits) % 32`,
but if --opt-level is given, `borrow` is always zero.
I wonder why this bug is not catched in the libstd's testsuite (I try the `rustc --test --opt-level=2 bigint.rs` before fixing the bug,
but the unittest passes normally.)
The existing adaptors like `map` in the `iter` module are very flawed because they only work for `BaseIter` implementations. There are many internal iterator implementations in the standard library like the set methods (`difference`, `symmetric_difference`, `intersection`, `union`) and the `range` functions that only share the `for` loop protocol in common.
The internal iterator adaptors should be implemented to work on any implementation of that protocol, rather than just a method called `each` taking `&self`.
This just moves `iter.rs` to `old_iter.rs` and begins work on documenting and implementing a nicer module.
r? @brson mkdir_recursive creates a directory as well as any of its
parent directories that don't exist already. Seems like a useful
thing to have in core.
(Or r? anyone who gets to it first.)
As part of the numeric trait reform (see issue #4819), I have added the following traits to `core::num` and implemented them for Rust's primitive numeric types:
~~~rust
pub trait Bitwise: Not<Self>
+ BitAnd<Self,Self>
+ BitOr<Self,Self>
+ BitXor<Self,Self>
+ Shl<Self,Self>
+ Shr<Self,Self> {}
pub trait BitCount {
fn population_count(&self) -> Self;
fn leading_zeros(&self) -> Self;
fn trailing_zeros(&self) -> Self;
}
pub trait Bounded {
fn min_value() -> Self;
fn max_value() -> Self;
}
pub trait Primitive: Num
+ NumCast
+ Bounded
+ Neg<Self>
+ Add<Self,Self>
+ Sub<Self,Self>
+ Mul<Self,Self>
+ Quot<Self,Self>
+ Rem<Self,Self> {
fn bits() -> uint;
fn bytes() -> uint;
}
pub trait Int: Integer
+ Primitive
+ Bitwise
+ BitCount {}
pub trait Float: Real
+ Signed
+ Primitive {
fn NaN() -> Self;
fn infinity() -> Self;
fn neg_infinity() -> Self;
fn neg_zero() -> Self;
fn is_NaN(&self) -> bool;
fn is_infinite(&self) -> bool;
fn is_finite(&self) -> bool;
fn mantissa_digits() -> uint;
fn digits() -> uint;
fn epsilon() -> Self;
fn min_exp() -> int;
fn max_exp() -> int;
fn min_10_exp() -> int;
fn max_10_exp() -> int;
fn mul_add(&self, a: Self, b: Self) -> Self;
fn next_after(&self, other: Self) -> Self;
}
~~~
Note: I'm not sure my implementation for `BitCount::trailing_zeros` and `BitCount::leading_zeros` is correct for uints. I also need some assistance creating appropriate unit tests for them.
More work needs to be done in implementing specialized primitive floating-point and integer methods, but I'm beginning to reach the limits of my knowledge. Please leave your suggestions/critiques/ideas on #4819 if you have them – I'd very much appreciate hearing them.
I have also added an `Orderable` trait:
~~~rust
pub trait Orderable: Ord {
fn min(&self, other: &Self) -> Self;
fn max(&self, other: &Self) -> Self;
fn clamp(&self, mn: &Self, mx: &Self) -> Self;
}
~~~
This is a temporary trait until we have default methods. We don't want to encumber all implementors of Ord by requiring them to implement these functions, but at the same time we want to be able to take advantage of the speed of the specific numeric functions (like the `fmin` and `fmax` intrinsics).
r? @brson
Unwinding through macros now happens as a call to the trait function `FailWithCause::fail_with()`, which consumes self, allowing to use a more generic failure object in the future.
The "unsigned 4 byte" `ub4`s are actually 8 bytes on 64-bit platforms
which mean that some bits > 2**32 were retained in calculations, these
would then "reappear" after a right shift and so the stream of random numbers
would differ on 32 bit vs 64 bit platforms.
http://burtleburtle.net/bob/c/randport.c
This removes the comparison to manual memory management examples,
because it requires too much existing knowledge. Implementing custom
destructors can be covered in the FFI tutorial, where `unsafe` is
already well explained.
This is a temporary trait until we have default methods. We don't want to encumber all implementors of Ord by requiring them to implement these functions, but at the same time we want to be able to take advantage of the speed of the specific numeric functions (like the `fmin` and `fmax` intrinsics).
This means that `ub4`s are always 4 bytes, rather than being 8 bytes on
x64. (Suggested but not implemented by upstream: "Porting it to a 64-bit
machine [...] may just need an adjustment of the definition of ub4")
Having three traits for primitive ints/uints seemed rather excessive. If users wish to specify between them they can simply combine Int with either the Signed and Unsigned traits. For example: fn foo<T: Int + Signed>() { … }
I didn't know how to use "use" initially, and an error message like this would
have solved quite a bit of frustration. I think this properly handles cases
where it's not appropriate but I'm not sure.
gifnksm