Functional programming of Swift (ii)-------thinking functionally

The main content of this article comes from the book "Functional Programming in Swift", a bit of a so-called post-view summary

In the introduction chapter of this book:

We'll try to focus on some of the qualities so we believe well-designed functional programs in Swift should exhibit:

1. Modulatity "Modular"

2. A careful treatment of Mutable State "take care of the variable condition": invariance and No side effects

3.Types "Type"

In fact, the above 3 points in my previous article has been described in detail.

thinking functionally -----Functional Programming idea, this is the second chapter of this book

Functions in Swift is first-class values

Below we illustrate the main contents of this chapter according to the examples in the book:

1. The first function we write, InRange1, checks. Checks if a point is within a range, relative to (0,0)

Determines whether the distance from the target point to the origin is <= range

Typealias Position = Cgpoint
Typealias Distance = Cgfloatfunc inRange1 (target:position, range:distance), Bool {    return sqrt (target.x * targe T.x + target.y * target.y) <= Range}

2. We Now add a argument representing the location of the ship to our InRange function:

The InRange method Adds a parameter that represents the position of the ship:

Determine if the distance between two points is <= range

Func inRange2 (target:position, Ownposition:position, range:distance), Bool {let    dx = ownposition.x-target.x Let    -dy = ownposition.y-target.y let    targetdistance = sqrt (dx * dx + dy * dy)     return targetdistance <= RA Nge

Now you realize that if target is too close to you, you need to avoid it. At this point, we define a minimumdistance to represent a safe distance.

Let Minimumdistance:distance = 2.0 func inRange3 (target:position, Ownposition:position, range:distance), Bool {
   let dx = ownposition.x-target.x let    dy = ownposition.y-target.y let    targetdistance = sqrt (dx * dx + dy * dy )     return targetdistance <= range && targetdistance >= minimumdistance}

Finally, you also need to escape from other ships that are closer to you.

Func inRange4 (target:position, Ownposition:position, Friendly:position, range:distance), Bool {let    dx = OWNP Osition.x-target.x let    -dy = ownposition.y-target.y let    targetdistance = sqrt (dx * dx + dy * dy) let    friend LYDX = friendly.x-target.x let    friendlydy = friendly.y-target.y let    friendlydistance = sqrt (FRIENDLYDX * frien DLYDX + friendlydy * friendlydy)    return targetdistance <= range              && targetdistance >= Minimumdistance              && (friendlydistance >= minimumdistance)}               

　　

　

　　

Functional programming of Swift (ii)-------thinking functionally