These constructions can be regarded as a weak form of currying based on data concatenation rather than function composition.
If the language provides a mechanism of futures or promises, then short-circuit evaluation can sometimes also be simulated in the context of a binary map operation.
The importance of this type-checking lies in the operator's most common use—in conditional assignment statements.
: operator is similar to the way conditional expressions (if-then-else constructs) work in functional programming languages, like Scheme, ML, Haskell, and XQuery, since if-then-else forms an expression instead of a statement in those languages.
Note that neither the true nor false portions can be omitted from the conditional operator without an error report upon parsing.
Rather than a conditional statement: the programmer could use the conditional expression to write more succinctly: Both ALGOL 68's choice clauses (if and the case clauses) provide the coder with a choice of either the "bold" syntax or the "brief" form.
[5] The behaviour is undefined if an attempt is made to use the result of the conditional operator as an lvalue.
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.
: operator forces the target of the assignment to be declared outside of the branches as a pointer, which can be freely rebound to different objects.
More generally speaking, keeping track of a nullable pointer increases cognitive load.
: operator conveys the semantics of Initializing a variable from only one of two choices based on a predicate appropriately.
: operator in CFML: Roughly 50% of the time the randRange() expression will return 1 (true) or 0 (false); meaning result will take the value "heads" or "tails" respectively.
Assignment using a conditional expression in Common Lisp: Alternative form: Example of using this operator in Crystal: Returns "false value".
The Crystal compiler transforms conditional operators to if expressions, so the above is semantically identical to: The Dart programming language's syntax belongs to the C family, primarily inspired by languages like Java, C# and JavaScript, which means it has inherited the traditional ?
If the System.Math library is used, the IfThen function returns a numeric value such as an Integer, Double or Extended.
Using System.Math Using the System.StrUtils library Usage example: Unlike a true ternary operator however, both of the results are evaluated prior to performing the comparison.
F# has a special case where you can omit the else branch if the return value is of type unit.
Used like booleanExp?then(whenTrue, whenFalse), fills the same role as the ternary operator in C-like languages.
[7] The built-in if-then-else syntax is inline: the expression has type The base library also provides the function Data.Bool.bool: In both cases, no special treatment is needed to ensure that only the selected expression is evaluated, since Haskell is non-strict by default.
There are also other variants that can be used, but they're generally more verbose: Luau, a dialect of Lua, has ternary expressions that look like if statements, but unlike them, they have no end keyword, and the else clause is required.
Thus, given a value of T for arg, the PHP code in the following example would yield the value horse instead of train as one might expect:[15] The reason is that nesting two conditional operators produces an oversized condition with the last two options as its branches: c1 ?
[17] To avoid this, nested parenthesis are needed, as in this example: This will produce the result of train being printed to the output, analogous to a right associative conditional operator.
In versions before Powershell 7 ternary operators are not supported [18] however conditional syntax does support single line assignment: In Powershell 7+ traditional ternary operators are supported and follow the C# syntax:[19] Though it had been delayed for several years by disagreements over syntax, an operator for a conditional expression in Python was approved as Python Enhancement Proposal 308 and was added to the 2.5 release in September 2006.
The traditional if-else construct in R (which is an implementation of S) is: If there is only one statement in each block, braces can be omitted, like in C: The code above can be written in the following non-standard condensed way: There exists also the function ifelse that allows rewriting the expression above as: The ifelse function is automatically vectorized.
With one conditional it is equivalent (although more verbose) to the ternary operator: This can be expanded to several conditionals: In addition to the standard CASE expression, MySQL provides an IF function as an extension: In addition to the standard CASE expression, SQL Server (from 2012) provides an IIF function: In addition to the standard CASE expression, Oracle has a variadic functional counterpart which operates similarly to a switch statement and can be used to emulate the conditional operator when testing for equality.
The ternary conditional operator of Swift is written in the usual way of the C tradition, and is used within expressions.
This allows the following example code to work: Using IIf, person.Name would be evaluated even if person is null (Nothing), causing an exception.
Zig uses if-else expressions instead of a ternary conditional operator:[25] Clearly the type of the result of the ?
The simplest benefit is avoiding duplicating the variable name, as in Python: instead of: More importantly, in languages with block scope, such as C++, the blocks of an if/else statement create new scopes, and thus variables must be declared before the if/else statement, as: Use of the conditional operator simplifies this: Furthermore, since initialization is now part of the declaration, rather than a separate statement, the identifier can be a constant (formally, of const type): When properly formatted, the conditional operator can be used to write simple and coherent case selectors.
The following are examples of notable general-purpose programming languages that don't provide a conditional operator: