Eval

Eval is a special programming function for meta-programming, with an interpreter (or the pair compiler / runtime system ) is instructed in the programming language itself written code fragment, which is present as a data object, to evaluate and to return the result of the calculation.

As well as any side effects such as the binding of a value to be considered a name, the programming language itself is " programmed " by Eval. The first programming language with this feature was LISP. Since the program code by inexperienced use of Eval can be hard to see through, grab many programmers depending on the application rather go back to more specific mechanisms such as macros or closures.

Eval is present among others in the programming languages ​​Perl, Bash, PHP, Javascript and Python.