Type theory is a big area. First of all, the term “types” is a kind of a misnomer in computer science, for a few reasons, even though they are mostly used for the same basic idea. Types have arisen in many contexts, philosophy, computer science, and mathematics, for mostly the same reasons. The origin of … Read more
It sounds like you’re asking about this error message: http://play.golang.org/p/h80rmDYCTI package main import “fmt” type A struct {} type B struct {} func (a *A) Foo() { fmt.Println(“A”) } func (b *B) Foo() { fmt.Println(“B”) } func main() { n := nil n.Foo() } This prints: prog.go:17: use of untyped nil [process exited with non-zero … Read more
Yes. You can simply write type MyInt = i32; These are aliases at the name level, i.e. it is absolutely immaterial which name for the same type you then use. They are perfectly interchangeable.
My usage can be divided into the following 5 categories. 1. interface 2. modularity 3. legibility 4. brevity 5. tricks If the variant type is only internal to the module, I use regular variants, because as you said they are compiled more efficiently. If the variant type is exported in the interface and I feel … Read more
With Kotlin 1.3+ you can use unsigned types. e.g. toUByte (Kotlin Playground): private fun magicallyExtractRightValue(b: Byte): Int { return b.toUByte().toInt() } or even require using UByte directly instead of Byte (Kotlin Playground): private fun magicallyExtractRightValue(b: UByte): Int { return b.toInt() } For releases prior to Kotlin 1.3, I recommend creating an extension function to do … Read more
As of Rust 1.50 you can use bool::then: assert_eq!(false.then(|| val), None); assert_eq!(true.then(|| val), Some(val)); You can convert it to a Result by chaining Option::ok_or: assert_eq!(false.then(|| val).ok_or(err), Err(err)); assert_eq!(true.then(|| val).ok_or(err), Ok(val)); As of Rust 1.62, you can use bool::then_some and pass a value directly instead of creating a closure: assert_eq!(false.then_some(val), None); assert_eq!(true.then_some(val), Some(val)); Alternatively, you can … Read more
Long story short, there’s no solution here that pleases everyone. Consider this common idiom: var customer = GetCustomer(…); // of type ‘Customer’ var address = customer && customer.address; if(address) { printAddressLabel(address); // Signature: (Address) => void } else { // Couldn’t find the customer or the customer has no address on file } It’d be … Read more
The most cautious thing you can do is to use TryFrom and panic when the value cannot fit within a usize: use std::convert::TryFrom; fn main() { let s = “abc”; let n: u32 = 1; let n_us = usize::try_from(n).unwrap(); let ch = s.chars().nth(n_us).unwrap(); println!(“{}”, ch); } By blindly using as, your code will fail in … Read more
Kotlin is designed to be fully interoperable with Java. Array<X> is X[] both at runtime and from Java’s point of view. Java arrays don’t implement Iterable, so Kotlin arrays (which are virtually the same) do not as well. We could make our arrays implement Iterable by creating a standalone class which does not relate to … Read more
It appears that the type <method-wrapper ..> is used by CPython for methods implemented in C code. Basically the type doesn’t wrap another method. Instead it wraps a C-implemented function as an bound method. In this way <method-wrapper> is exactly like a <bound-method> except that it is implemented in C. In CPython there are two … Read more