En - Chapter 1 - General Discussion

8/21/2019 En - Chapter 1 - General Discussion

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Friendly F#

Functional languages applied to

videogames


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Introduction

Real (and fun) applications

Physics simulations

Videogames

... No factorials!

Problemsolution approach


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Agenda

Chapter Application Constructs

1 Bouncing ball Control flow, tuples, functions

2 Rocket Saturn V Basic data structures (record),units of measure

3 Asteroid field Lists and sequences

4 Bigger asteroid field Trees and discriminated unions


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Chapter 1

Basic Data Manipulation


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Preliminar notes

Indentation is part of the code

Spaces matter!

Modules and namespaces

Block of names with the same prefix

Modules also contain values, namespaces only

type declarations

Can be nested


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General discussion (*)

Constructs

Let

Functions

Higher order

Recursive

Partially specialized

Generic types Conditional expressions

Imperative capabilities


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Let binding and functions (*)

let pi = 3.141592654

let a,b,c = 1,20.0,"hello"

let a' = 2+a*3


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let f x =

Console.Write(x.ToString())

x*3+1

let y = f 2

let y = f 4

let x = 2


let y = x*3+1

let x = 4


let y = x*3+1


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let FUNCTION-NAME PARAMS = BODY

let incr x = x+1

fun PARAMS -> BODY

let res = (fun x -> x*2+1) 10


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let f'' g = g 10 (int -> int) -> int

let res1 = f'' (fun x -> x*2+1)

let res2 = f'' incr


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let rec factorial n =

if n = 0 then 1

else n*factorial (n-1)


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let f() =

let x = 10let x = "hello"

x


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let f'() =

let x = 10

let g() = printf "%d\n" xlet x = "hello"

do g()

x


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Branching and Matching (*)

Code branches

If-then-else Pattern matching


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if cond then

BRANCH1

else

BRANCH2


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Boolean values

True

False

Bool type

Operators

Or, And, Not


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Examples

let i = if p then 10 else 20let j = if q || r then "hello" else "ciao"

let k = if i < 10 then "thank you" else

(if i < 20 then "grazie" else "merci")


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Nested ifs

Indentation is essential

let k = if i < 10 then"thank you"

else

if i < 20 then

"grazie"

else"merci"


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Elif

let k = if i < 10 then"thank you"

elif i < 20 then

"grazie"

else

"merci"


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Types

If has the same type of its branches

Both branches must have the same type

Not allowed

if i > 10 then "hello" else 20


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Pattern Matching

let rec fibonacci n =

if n = 0 then 0

elif n = 1 then 1else fibonacci (n-1)+fibonacci (n-2)

let rec fibonacci' n =

match n with| 0 -> 0

| 1 -> 1

| v -> fibonacci' (v-1)+fibonacci' (v-2)


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Function

let f x =

match x with...

let f =

function...


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Variables and statements (*)

Imperative constructs

Variables

References

For and while loops

...


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Variables

Local mutable cells

Heap-allocated references

let mutable v1 = 0

let v2 = ref 0

do v1


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References: generic type

Assignments: type unit

val v1 : int

val v2 : int ref


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For loop

NB: extremes included!

for i = x to y do BODY


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Generic functions and partial

specialization (**)

Partially specialized functions

Some parameters are stored in advance

Result: function with less parameters

Generic functions

Parameters of (almost) any type


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specialization (**)

Ref is a generic type

let quadratic_int (a,b,c,x) = a*x*x+b*x+c

let quadratic_float (a:float,b,c,x) =

a*x*x+b*x+c

let quadratic (sum,prod,a,b,c,x) =let x_square = prod(x,x)

let t1 = prod(x_square,a)

let t2 = prod(x,b)

sum(sum(t1,t2),c)


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specialization (**)

a = any type

val quadratic : ('a*'a ->

'a)*('a*'a -> 'a)*'a*'a*'a*'a -> 'a

let y1 = quadratic

((fun (x,y) -> x+y),(fun (x,y) -> x*y),10,4,-2,3)

let y2 = quadratic

((fun (x,y) -> x+y),(fun (x,y) -> x*y),

10 0 4 0 -2 0 3 0)

En - Chapter 1 - General Discussion

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