Expression Versus Statement

Question

I\'m asking with regards to c#, but I assume its the same in most other languages.

Does anyone have a good definition of expressions and statements

Answer 1

I am not really satisfied with any of the answers here. I looked at the grammar for C++ (ISO 2008). However maybe for the sake of didactics and programming the answers might suffice to distinguish the two elements (reality looks more complicated though).

A statement consists of zero or more expressions, but can also be other language concepts. This is the Extended Backus Naur form for the grammar (excerpt for statement):

statement:
        labeled-statement
        expression-statement <-- can be zero or more expressions
        compound-statement
        selection-statement
        iteration-statement
        jump-statement
        declaration-statement
        try-block

We can see the other concepts that are considered statements in C++.

• expression-statements is self-explaining (a statement can consist of zero or more expressions, read the grammar carefully, it's tricky)
• case for example is a labeled-statement
• selection-statements are if if/else, case
• iteration-statements are while, do...while, for (...)
• jump-statements are break, continue, return (can return expression), goto
• declaration-statement is the set of declarations
• try-block is statement representing try/catch blocks
• and there might be some more down the grammar

This is an excerpt showing the expressions part:

expression:
        assignment-expression
        expression "," assignment-expression
assignment-expression:
        conditional-expression
        logical-or-expression assignment-operator initializer-clause
        throw-expression

• expressions are or contain often assignments
• conditional-expression (sounds misleading) refers to usage of the operators (+, -, *, /, &, |, &&, ||, ...)
• throw-expression - uh? the throw clause is an expression too