Since mutability breaks referential transparency, referentially transparent expressions can only work with immutable data structures.
While the communities of many of the newer (and some of the older) programming languages start to appreciate the benefits of programming in a pure, referentially transparent fashion, these concepts have not yet had a big impact on software used in chemistry.
One programming paradigm that greatly facilitates writing referentially transparent functions and using immutable data structures is the one of functional programming.
Although programming in a type-safe and referentially transparent style offers several advantages over working with mutable data structures and side effects, this style of programming has not seen much use in chemistry-related software.
An expression in a program is said to be referentially transparent when all it does is calculating its result from its input parameters (possibly by calling other referentially transparent functions) and nothing else.
FOBS is a dynamically typed, referentially transparent language, designed for use as a universal scripting language.
PEGs are referentially transparent, allowing common subexpressions to be identified and allowing equalities to propagate via congruence closure.
In contrast, most verbs, such as visit, are "referentially transparent"; if someone visits the morning star, then it follows that he visits the evening star.
An expression that contains only pure function calls is referentially transparent; its value does not change if we substitute one of its subexpression with the value of that subexpression.
The standard view, then, takes belief-attributing sentences to be systematically ambiguous between a referentially opaque, de dicto structure and a referentially transparent, de re structure.
In an expression, a call to a referentially transparent function can always be replaced with the function's result for the given set of parameters without altering the behavior of the program.
