Search results
Results From The WOW.Com Content Network
The dangling else is a problem in programming of parser generators in which an optional else clause in an if–then(–else) statement can make nested conditional statements ambiguous.
An important use of the conditional operator is in allowing a single initialization statement, rather than multiple initialization statements. In many cases this also allows single assignment and for an identifier to be a constant. The simplest benefit is avoiding duplicating the variable name, as in Python:
Conditional statements can be and often are nested inside other conditional statements. Some languages allow ELSE and IF to be combined into ELSEIF , avoiding the need to have a series of ENDIF or other final statements at the end of a compound statement.
If-then-else flow diagram A nested if–then–else flow diagram. In computer science, conditionals (that is, conditional statements, conditional expressions and conditional constructs) are programming language constructs that perform different computations or actions or return different values depending on the value of a Boolean expression, called a condition.
In many languages, the else in an If–then(–else) statement is optional, which results in nested conditionals having multiple ways of being recognized in terms of the context-free grammar. Concretely, in many languages one may write conditionals in two valid forms: the if-then form, and the if-then-else form – in effect, making the else ...
That is, a statement such as x = expression; (i.e. the assignment of the result of an expression to a variable) clearly calls for the expression to be evaluated and the result placed in x, but what actually is in x is irrelevant until there is a need for its value via a reference to x in some later expression whose evaluation could itself be ...
would assign null to theWidth if either "Main" or the fifth subview is missing, or complete the statement and return the width if they are both valid. There are many times where the programmer wants to take different actions in these two cases, so Swift adds another form of syntactic sugar for this role, the if let statement, also known as "optional binding":
Equivalent to the switch statement found in some programming languages, it is a convenient way of dealing with multiple cases without having to chain lots of #if functions together. However, note that performance suffers when there are more than 100 alternatives.