Editing Statement (computer science) (section)

==Expressions==
A distinction is often made between statements, which are executed, and [[expression (programming)|expression]]s, which are evaluated. Expressions always evaluate to a value, which statements do not. However, expressions are often used as part of a larger statement.

In most programming languages, a statement can consist of little more than an expression, usually by following the expression with a statement terminator (semicolon). In such a case, while the expression evaluates to a value, the complete statement does not (the expression's value is discarded). For instance, in C, C++, C#, and many similar languages, <code>x = y + 1</code> is an expression that will set x to the value of y plus one, and the whole expression itself will evaluate to the same value that x is set to. However, <code>x = y + 1;</code> (note the semicolon at the end) is a statement that will still set x to the value of y plus one because the expression within the statement is still evaluated, but the result of the expression is discarded, and the statement itself does not evaluate to any value.<ref>{{Cite web |title=ISO/IEC 9899:1999 (E) |url=https://www.dii.uchile.cl/~daespino/files/Iso_C_1999_definition.pdf |url-status=live |archive-url=https://web.archive.org/web/20240207035551/http://www.dii.uchile.cl/~daespino/files/Iso_C_1999_definition.pdf |archive-date=Feb 7, 2024 |website=ISO/IEC}}</ref>

Expressions can also be contained within other expressions. For instance, the expression <code>x = y + 1</code> contains the expression <code>y + 1</code>, which in turn contains the values <code>y</code> and <code>1</code>, which are also technically expressions.

Although the previous examples show assignment expressions, some languages do not implement assignment as an expression, but rather as a statement. A notable example of this is [[Python (Programming Language)|Python]], where = is not an operator, but rather just a separator in the assignment statement. Although Python allows multiple assignments as each assignment were an expression, this is simply a special case of the assignment statement built into the language grammar rather than a true expression.<ref>{{cite web | url=https://docs.python.org/3/reference/simple_stmts.html#assignment-statements | title=7. Simple statements |work=Python 3.10.8 documentation }}</ref>