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immutable is a stronger variant of const, indicating data that can never change its value, while const indicates data that cannot be changed through this reference: it is a constant view on possibly mutable data. shared is used for shared data in multi-threading (as volatile was briefly used for in C++).
Exceptions provide a form of non-local control flow, in that an exception may "bubble up" from a called function. This bubbling can cause an exception safety bug by breaking invariants of a mutable data structure, as follows: [7] A step of an operation on a mutable data structure modifies the data and breaks an invariant.
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).
Unlike ordinary C function definitions, their value can capture state from their surrounding context. A block definition produces an opaque value which contains both a reference to the code within the block and a snapshot of the current state of local stack variables at the time of its definition.
Example side effects include modifying a non-local variable, a static local variable or a mutable argument passed by reference; raising errors or exceptions; performing I/O; or calling other functions with side-effects. [1] In the presence of side effects, a program's behaviour may depend on history; that is, the order of evaluation matters.
The names "lambda abstraction", "lambda function", and "lambda expression" refer to the notation of function abstraction in lambda calculus, where the usual function f (x) = M would be written (λx. M), and where M is an expression that uses x. Compare to the Python syntax of lambda x: M.
The state of an object cannot be changed after construction. This implies both that only read-only data is shared and that inherent thread safety is attained. Mutable (non-const) operations can then be implemented in such a way that they create new objects instead of modifying the existing ones.
Conversely, the mutable keyword allows a class member to be changed even if an object was instantiated as const. Even functions can be const in C++. The meaning here is that only a const function may be called for an object instantiated as const; a const function doesn't change any non-mutable data.