![]() The syntaxes of the tokens are similar: If(, op1, op2) vs IIf(condition, op1, op2). As a true operator, it does not have the side effects and potential inefficiencies of the IIf() function. Visual Basic Version 9 has added the operator If() in addition to the existing IIf() function that existed previously. With a true short-circuiting conditional operator, person.Name is not evaluated unless person is not null. Using IIf, person.Name would be evaluated even if person is null (Nothing), causing an exception. This last is true for reference types, for example:ĭim name As String = If ( person Is Nothing, "", person. Bear in mind also that some types allow initialization, but do not allow assignment, or even that the assignment operator and the constructor do totally different things. For example, to pass conditionally different values as an argument for a constructor of a field or a base class, it is impossible to use a plain if-else statement in this case we can use a conditional assignment expression, or a function call. In such case it is always possible to use a function call, but this can be cumbersome and inelegant. In C++ there are conditional assignment situations where use of the if-else statement is impossible, since this language explicitly distinguishes between initialization and assignment. This means that expressions like q ? a : b = c and (q ? a : b) = c are both legal and are parsed differently, the former being equivalent to q ? a : (b = c). Unlike in C, the precedence of the ?: operator in C++ is the same as that of the assignment operator ( = or OP=), and it can return an lvalue. If the language does not permit side-effects in expressions (common in functional languages), then the order of evaluation has no value semantics-though it may yet bear on whether an infinite recursion terminates, or have other performance implications (in a functional language with match expressions, short-circuit evaluation is inherent, and natural uses for the ternary operator arise less often, so this point is of limited concern).įor these reasons, in some languages the statement form variable = condition ? expr1 : expr2 can have subtly different semantics than the block conditional form if (condition) C++ If the language supports expressions with side effects but does not specify short-circuit evaluation, then a further distinction exists about which expression evaluates first-if the language guarantees any specific order (bear in mind that the conditional also counts as an expression).įurthermore, if no order is guaranteed, a distinction exists about whether the result is then classified as indeterminate (the value obtained from some order) or undefined (any value at all at the whim of the compiler in the face of side effects, or even a crash). The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language.Ī top level distinction from one language to another is whether the expressions permit side effects (as in most procedural languages) and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated (most standard operators in most languages evaluate all arguments). Īlthough many ternary operators are possible, the conditional operator is so common, and other ternary operators so rare, that the conditional operator is commonly referred to as the ternary operator. It originally comes from CPL, in which equivalent syntax for e 1 ? e 2 : e 3 was e 1 → e 2, e 3. ![]() ![]() NET, it instead takes the form If(a, b, c). The form a ? b : c is by far and large the most common, but alternative syntaxes do exist for example, Raku uses the syntax a ? b !! c to avoid confusion with the infix operators ? and !, whereas in Visual Basic. One can read it aloud as "if a then b otherwise c". An expression a ? b : c evaluates to b if the value of a is true, and otherwise to c. It is commonly referred to as the conditional operator, ternary if, or inline if (abbreviated iif). In computer programming, the ternary conditional operator is a ternary operator that is part of the syntax for basic conditional expressions in several programming languages. For use as a binary operator, see Elvis operator.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |