I. Introduction

1. What are the main characteristics of all the Functional Programming Languages (F#, Javascript, Python, (CA)ML, Lisp, Haskell,...) ?

• Based on a paradigm (point of view) where everything is a function

Ex. What is the "factorial" function ? What is the derivative of a function ?

• Based on a simple mathematical model with rewriting: the lambda calculus with only "substitutions" as illustrated here

$$ (fun\ x\to y)\ v \Leftrightarrow y[x/v] $$

NB. A common syntactic sugar of the preceding expression is: "let x=v in y"

2. Different from imperative (e.g. computing factorial):

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