science

Ternary conditional operator

Ternary conditional operator is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ternary conditional operator rather than just read about it. In short: In computer programming, the ternary conditional operator is a conditional expression with three parts: the Boolean condition, the then-expression, and the else-expression. If the condition is true, the then-expression is evaluated; otherwise, the else-expression is evaluated; and the value is returned.

Key takeaways

Ternary conditional operator belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ternary conditional operator to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ternary conditional operator from memory before moving on to harder problems.

Reference excerpt

In computer programming, the ternary conditional operator is a conditional expression with three parts: the Boolean condition, the then-expression, and the else-expression. If the condition is true, the then-expression is evaluated; otherwise, the else-expression is evaluated; and the value is returned. Thus it is a non-strict operator, like other conditional expressions. It is also called a conditional operator, ternary if, immediate if, or inline if (iif). Although a ternary operator in general is any operator with three arguments, the three-argument conditional operator is the only common one in programming, so it is loosely called the ternary operator. C introduced the syntax a ? b : c, read as "if a then b otherwise c", which is widely used by other languages with C-like syntax. Some languages use functional syntax: in Visual Basic, it is written If(a, b, c). Many languages support conditional expressions with two, three, or more clauses. Languages following ALGOL-like syntax often support them with the same syntax as conditional statements, if a then b else c. The construct first appeared in CPL in 1963, as a → b, c.

Patterns

Assignment The value of the operator can be assigned to a variable. For a weakly typed language, the data type of the selected value may determine the type of the assigned value. For a strongly typed language, both value expressions must evaluate to a type that is compatible with the target variable. The operator is similar to the way conditional expressions (if-then-else) 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. The operator allows for initializing a variable via a single statement which otherwise might require multiple statements. Use in variable assignment reduces the probability of a bug from a faulty assignment as the assigned variable is stated only once. For example, in Python:

instead of:

In a language with block scope, a variable must be declared before the if-else statement. For example:

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. For example:

Case selector The conditional operator can be used for case selectors. For example:

Variations The syntax and semantics of the operator vary by language. Major differences include whether the expressions can have side effects and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated. If a language supports expressions with side effects but does not specify short-circuit evaluation, then a further distinction exists about which expression evaluates first. 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). If a 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). For these reasons, in some languages the statement form r = condition ? expr1 : expr2 can have subtly different semantics than the block conditional form if (condition) { r = expr1; } else { r = expr2; }. In almost all languages, the ternary operator is right associative, so that a == 1 ? "one" : a == 2 ? "two" : "many" evaluates intuitively as a == 1 ? "one" : (a == 2 ? "two" : "many"). This means it can be chained similarly to an if ... else if ... else if ... else chain. The main exception is PHP, in which it was left-associative (such that the same expression evaluates to (a == 1 ? "one" : a == 2) ? "two" : "many", which is rarely what the programmer expects) prior to version 8, and is non-associative thereafter. Furthermore, in all C-family languages and many others, the ternary conditional operator has low operator precedence.

Examples

Ada The 2012 edition of Ada introduced conditional expressions (using if and case), as part of an enlarged set of expressions including quantified expressions and expression functions. The Rationale for Ada 2012 states motives for Ada not having had them before, as well as motives for now adding them, such as to support "contracts" (also new).

When the value of an if_expression is itself of Boolean type, then the else part may be omitted, the value being True. Multiple conditions may chained using elsif.

ALGOL 60 ALGOL 60 introduced conditional expressions (ternary conditionals) to imperative programming languages. This conditional statement:

Can be rewritten with the conditional operator:

ALGOL 68 Both ALGOL 68's choice clauses (if and case clauses) support the following:

Single if choice clause if condition then statements [ else statements ] fi or a brief form: ( condition | statements | statements ) Chained if choice clause if condition1 then statements elif condition2 then statements [ else statements ] fi or a brief form: ( condition1 | statements |: condition2 | statements | statements ).

Bash A true ternary operator exists for arithmetic expressions:

For strings there are workarounds, like e.g.:

Where condition can be any bash command. When it exits with success, the first echo command is executed, otherwise the second one is executed.

C family The following code in C assigns result to the value of x if a > b, and otherwise to the value of y. This is the same syntax as in many related languages including C++, Java, JavaScript, and Dart.

Only the selected expression is evaluated. In this example, x and y require no evaluation, but they can be expressions with side effects. Only the side-effect for the selected expression value will occur. If x and y are of the same data type, the conditional expression generally has that type. Otherwise, the rules governing the resulting data type vary a little between languages:

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Ternary conditional operator

Start with the simplest possible case. Write down what Ternary conditional operator claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ternary conditional operator before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ternary conditional operator ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ternary conditional operator

In research: Ternary conditional operator appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ternary conditional operator in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ternary conditional operator is common in secondary-school and first-year university syllabi. It links to neighbouring topics Conditional constructs, Operators (programming), Ternary operations, so understanding it makes those chapters shorter.
In everyday life: Look for Ternary conditional operator outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ternary conditional operator in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ternary conditional operator means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ternary conditional operator out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ternary conditional operator in simple terms?

Why does Ternary conditional operator matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ternary conditional operator?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ternary conditional operator.