# Definitions Syntax : The set of rules that defines the combinations of symbols that are recogized as sentences. Semantics : Defines what programs do when executed.

## Linguistic abstraction Abstraction and addition to a language, by using already existing concepts of the language _Example:_ use `proc` to define `fun` ## Declarative programs - stateless - independt - deterministic In other words, every time you run a declarative program with the same input (or just a declarative component) it will give you the same result (i.e. output). ## Observal declarativity A component can be seen as declarative if the definition is, even though the implementation is not _Example:_ A database with a declarative interface. ## Higher-order programming Use procedure values in programs. (E.g. pass procedures as arguments to other procedures) __Closure__ = procedure value. Four basic operations underlie all techniques in higher order programming ### Procedural abstraction Any statement can be put into a procedure. ### Genericity The ability to pass procedure values as arguments to a procedure call. ### Instatiation The ability to return procedure values as results from a procedure call. ### Embedding Put procedure values in data structures