D programming Language
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- Navigate this page:
- Labelled Statements
- Block Statement
- Expression Statement
- Declaration Statement
- If Statement
- While Statement
StatementsC and C++ programmers will find the D statements very familiar, with a few interesting additions. Statement: LabeledStatement BlockStatement ExpressionStatement DeclarationStatement IfStatement DebugStatement VersionStatement WhileStatement DoWhileStatement ForStatement SwitchStatement CaseStatement DefaultStatement ContinueStatement BreakStatement ReturnStatement GotoStatement WithStatement SynchronizeStatement TryStatement ThrowStatement VolatileStatement AsmStatement
Labelled StatementsStatements can be labelled. A label is an identifier that precedes a statement. LabelledStatement: Identifier ':' Statement Any statement can be labelled, including empty statements, and so can serve as the target of a goto statement. Labelled statements can also serve as the target of a break or continue statement. Labels are in a name space independent of declarations, variables, types, etc. Even so, labels cannot have the same name as local declarations. The label name space is the body of the function they appear in. Label name spaces do not nest, i.e. a label inside a block statement is accessible from outside that block.
A block statement introduces a new scope for local symbols. A local symbol's name, however, must be unique within the function. void func1(int x) { int x; // illegal, x is multiply defined in function scope }
{ int x; { int x; // illegal, x is multiply defined in function scope } } void func3() { { int x; } { int x; // illegal, x is multiply defined in function scope } }
{ { int x;
} { x++; // illegal, x is undefined } }
Expression StatementThe expression is evaluated. ExpressionStatement: Expression ; Expressions that have no affect, like (x + x), are illegal in expression statements.
Declaration StatementDeclaration statements declare and initialize variables. DeclarationStatement: Type IdentifierList ; IdentifierList: Variable Variable , IdentifierList Variable: Identifier Identifier = AssignmentExpression If no AssignmentExpression is there to initialize the variable, it is initialized to the default value for its type.
If StatementIf statements provide simple conditional execution of statements. IfStatement: if ( Expression ) Statement if ( Expression ) Statement else Statement Expression is evaluated and must have a type that can be converted to a boolean. If it's true the if statement is transferred to, else the else statement is transferred to. The 'dangling else' parsing problem is solved by associating the else with the nearest if statement.
While StatementWhile statements implement simple loops. WhileStatement: while ( Expression ) Statement Expression is evaluated and must have a type that can be converted to a boolean. If it's true the statement is executed. After the statement is executed, the Expression is evaluated again, and if true the statement is executed again. This continues until the Expression evaluates to false. A break statement will exit the loop. A continue statement will transfer directly to evaluationg Expression again.
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