Cast is explicit. Coerce is implicit. The examples in Python would be: cast(2, POINTER(c_float)) #cast 1.0 + 2 #coerce 1.0 + float(2) #conversion Cast really only comes up in the C FFI. What is typically called casting in C or Java is referred to as conversion in python, though it often gets referred to as … Read more
Ah, I just remembered the identity meta-function. It is possible to write operator typename identity<void (Testable::*)() const>::type() const; with the following definition of identity: template <typename T> struct identity { typedef T type; }; You could argue that identity still uses a typedef, but this solution is “good” enough for me.
Javascript now supports a null-coalescing operator: ??. It may not be production-ready (consult the support table), but it’s certainly safe to use with Node or a transpiler (TypeScript, Babel, etc.). Per MDN, The nullish coalescing operator (??) is a logical operator that returns its right-hand side operand when its left-hand side operand is null or … Read more
I didn’t really understood from Rayon answer how valueOf and toString come into play when converting an object to a primitive value; so I dug into the ECMAScript 2015 specifications. Warning: Long answer. We want to check the expression 1 == [1]. Starting from the 12.10 Equality Operators we see that, after retrieving the expressions … Read more
[T; n] is an array of length n, represented as n adjacent T instances. &[T; n] is purely a reference to that array, represented as a thin pointer to the data. [T] is a slice, an unsized type; it can only be used through some form of indirection. &[T], called a slice, is a sized … Read more
Short answer: check out how Matrix is doing it. The idea is that coerce returns [equivalent_something, equivalent_self], where equivalent_something is an object basically equivalent to something but that knows how to do operations on your Point class. In the Matrix lib, we construct a Matrix::Scalar from any Numeric object, and that class knows how to … Read more
This works: (apply str my-char-seq) Basically, str calls toString() on each of its args and then concatenates them. Here we are using apply to pass the characters in the sequence as args to str.
Use the names function: whatyouwant <- as.character(dd$name) names(whatyouwant) <- dd$crit as.character is necessary, because data.frame and read.table turn characters into factors with default settings. If you want a one-liner: whatyouwant <- setNames(as.character(dd$name), dd$crit)