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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.
The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language. A 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 ...
In this example, s is unambiguously executed when a is true and b is true, but one may interpret s2 as being executed when a is false (thus attaching the else to the first if) or when a is true and b is false (thus attaching the else to the second if). In other words, one may see the previous statement as either of the following expressions:
In this example, because someCondition is true, this program prints "1" to the screen. Use the ?: operator instead of an if-then-else statement if it makes your code more readable; for example, when the expressions are compact and without side-effects (such as assignments).
The corresponding logical symbols are "", "", [6] and , [10] and sometimes "iff".These are usually treated as equivalent. However, some texts of mathematical logic (particularly those on first-order logic, rather than propositional logic) make a distinction between these, in which the first, ↔, is used as a symbol in logic formulas, while ⇔ is used in reasoning about those logic formulas ...
Add #elifdef and #elifndef directives, [16] which are essentially equivalent to #elif defined and #elif !defined. Both directives were added to C++23 standard and GCC 12. [17] Add #embed directive for binary resource inclusion and __has_embed allowing the availability of a resource to be checked by preprocessor directives. [18]
The example code tests if a macro __unix__ is defined. If it is, the file <unistd.h> is then included. Otherwise, it tests if a macro _WIN32 is defined instead. If it is, the file <windows.h> is then included. A more complex #if example can use operators; for example:
When investigating the possibility of removing friend name injection from the C++ programming language, Barton and Nackman's idiom was found to be the only reasonable use of that language rule. Eventually, the rules for argument-dependent lookup were adjusted [ 2 ] to replace friend name injection by a less drastic mechanism, described above ...