All its methods return functions, while in an imperative implementation using mutable state their return type would be Unit (similar to void in Java).
Where imperative programming relies heavily on mutable state (changing an object's value during execution), functional programming focuses on immutable state, in which a declared object retains its value throughout the process.
To support optimizations in classic imperative style, we built a control-flow graph using mutable pointers and other mutable state in the nodes.
A referentially transparent function may not access or alter mutable state, nor may it perform any other form of side-effects.
If it is necessary to mention evaluation order, such as when the context discusses mutable state, say that the expression "evaluates to" a value.
In this manner, actors allow mutable state to be shared between multiple tasks in a way that remote functions do not.
We present a realizability model for reasoning about contextual equivalence of higher-order programs with impredicative polymorphism, recursive types, and higher-order mutable state.
However, parallelism introduces new challenges in writing correct code, particularly in the presence of shared, mutable state.
For problems that can be solved efficiently in the functional model, with no shared mutable state, parallelism poses few problems.
Recent models and logics for shared-memory programs with mutable state and pointers build on and extend Park's foundations, with emphasis on resources and logical rules that embody separation principles.
However, we found that CDK's parser is not referentially transparent and operates on mutable state internally.
