# FLC - lesson 04
##### Luca Oddone Breveglieri
###### 12 october 2015
##Lists

#### Linguistic Abstraction //Optional
Transforms the phrases of a real language and gives them an __abstract representation__  
> At the abstract level, the typical structures...

#### Substitution operation
Replaces the terminal characters of the source language with the phrases of the target language.

#### Nested Lists
Lists may contain:
- atomic objects
- Other lists of *lower level*

## Grammars
Are meant to overcome the limits of regexp
Are composed by:
- a startin language
- a set of rules which can be applied a finite number of times.

#### Context-free Grammars
Is a generalization of regexp