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Both Proc.new and lambda in this example are ways to create a closure, but semantics of the closures thus created are different with respect to the return statement. In Scheme, definition and scope of the return control statement is explicit (and only arbitrarily named 'return' for the sake of the example). The following is a direct translation ...
Read-only data types (sources) can be covariant; write-only data types (sinks) can be contravariant. Mutable data types which act as both sources and sinks should be invariant. To illustrate this general phenomenon, consider the array type. For the type Animal we can make the type Animal [], which is an "array of animals". For the purposes of ...
Like function definitions, blocks can take arguments, and declare their own variables internally. 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 ...
In computing, a persistent data structure or not ephemeral data structure is a data structure that always preserves the previous version of itself when it is modified. Such data structures are effectively immutable , as their operations do not (visibly) update the structure in-place, but instead always yield a new updated structure.
There are multiple ways to implement the flyweight pattern. One example is mutability: whether the objects storing extrinsic flyweight state can change. Immutable objects are easily shared, but require creating new extrinsic objects whenever a change in state occurs. In contrast, mutable objects can share state.
For example ((call/cc f) e2) is equivalent to applying f to the current continuation of the expression. The current continuation is given by replacing (call/cc f) by a variable c bound by a lambda abstraction, so the current continuation is (lambda (c) (c e2)). Applying the function f to it gives the final result (f (lambda (c) (c e2))).
The immutable keyword denotes data that cannot be modified through any reference. The const keyword denotes a non-mutable view of mutable data. Unlike C++ const, D const and immutable are "deep" or transitive, and anything reachable through a const or immutable object is const or immutable respectively. Example of const vs. immutable in D
In the spirit of imperative programming, an abstract data structure is conceived as an entity that is mutable—meaning that there is a notion of time and the ADT may be in different states at different times. Operations then change the state of the ADT over time; therefore, the order in which operations are evaluated is important, and the same ...