In Kotlin, if statements are expressions. So the following code is equivalent: if (a) b else c The distinction between expression and statement is important here. In Java/C#/JavaScript, if forms a statement, meaning that it does not resolve to a value. More concretely, you can’t assign it to a variable. // Valid Kotlin, but invalid … Read more
I tested the following page in Tomcat 5.59, JSP 2.0 and JSTL 1.1. It ran without any errors. <%@taglib uri=”http://java.sun.com/jsp/jstl/core” prefix=”c”%> <c:set var=”value” scope=”request” value=”someValue”/> <c:out default=”None” escapeXml=”true” value=”${not empty value ? value : ‘None’}” /> <c:out default=”None” escapeXml=”true” value=”${empty value ? ‘None’ : value}” /> <c:set var=”value” scope=”request” value=”” /> <br/> <c:out default=”None” escapeXml=”true” … Read more
Both i and j are glvalues (see this value category reference for details). Then if you read this conditional operator reference we come to this point: 4) If E2 and E3 are glvalues of the same type and the same value category, then the result has the same type and value category So the result … Read more
The compiler requires that either the types of second and third operands are the same, or that one is implicitly convertible to the other. In your case, the types are DBNull and string, neither of which is implicitly convertible to the other. Casting either of them to object solves that. EDIT: Looks like it is … Read more
From http://en.wikipedia.org/wiki/%3F%3A A GNU extension to C allows omitting the second operand, and using implicitly the first operand as the second also: a = x ? : y; The expression is equivalent to a = x ? x : y; except that if x is an expression, it is evaluated only once. The difference is … Read more
This is permitted in GNU as an obscure extension to C 5.7 Conditionals with Omitted Operands The middle operand in a conditional expression may be omitted. Then if the first operand is nonzero, its value is the value of the conditional expression. Therefore, the expression x ? : y has the value of x if … Read more
If it evaluated from left to right, it’d look like this: z = ((a == b ? a : b) ? c : d); That is, it would use the result of the first conditional (a or b) as the boolean condition of the second conditional. That doesn’t make much sense: that’s like saying: int … Read more
You need to read section 15.25 of the Java Language Specification. In particular: Otherwise, if the second and third operands have types that are convertible (ยง5.1.8) to numeric types, then there are several cases: If one of the operands is of type byte or Byte and the other is of type short or Short, then … Read more
You can do: someBool = (someStatement) ? true : someBool; I don’t think that gains you a lot of clarity over: if (someStatement) { someBool = true; } But it really seems to be a matter of taste. I wouldn’t say either is clearly bad, but the former is uncommon, so I’d probably avoid it. … Read more
When you write value = condition ? null : 1.0; the type of condition ? null : 1.0 must be a reference type, so the type is Double, which can hold the value null. When you write value = condition ? getDouble() : 1.0; and getDouble() returns null, it’s equivalent to writing: value = condition … Read more