class vec2d{
constructor() {
var argLen = arguments.length;
var tmp_x, tmp_y;
// 1st. argument an array => construct the vector given an array of coordinates
if (arguments[0] instanceof Array) {
if (arguments[0].length < 2) throw "Not enough coordinates in array";
tmp_x = arguments[0][0];
tmp_y = arguments[0][1];
// 1st. arg. not an array => each arg a coordiante
} else {
if (arguments.length < 2) throw "Not enough coordinates";
tmp_x = arguments[0];
tmp_y = arguments[1];
};
if (typeof(tmp_x)!="number" || typeof(tmp_y)!= "number") throw "both coordinates must be numbers!";
this._x = tmp_x;
this._y = tmp_y;
};
getTxt(r=0) {return this._x.toFixed(r)+ ',' + this._y.toFixed(r)}
toString() {return '[Vector (' + this.getTxt() + ')]'}
getArray() {return [ this._x, this._y ]}
add(v) {
if (!(v instanceof vec2d)) throw "add(v) : v must be a vec2d";
return new this.constructor( this._x + v._x, this._y + v._y );
}
scale(s) { // dot product
if (typeof(s)!="number" || isNaN(s)) throw "scale(s) : s must be a number";
return new this.constructor( this._x*s, this._y*s);
}
sub(v) {
if (!(v instanceof vec2d)) throw "sub(v) : v must be a vec2d";
return this.add(v.scale(-1));
}
dot(v) { // dot product
if (!(v instanceof vec2d))throw "dot(v) : v must be a vec2d";
return ( this._x * v._x + this._y * v._y );
}
xprod(v) { // z of the (would be 3D) tensor multiplication, if input z = const(0)
if (!(v instanceof vec2d)) throw "xprod(v) : v must be a vec2d";
return ( this._x * v._y - this._y * v._x );
}
len(e) { // length of the vector
if (typeof e == 'number') {
let now = this.len()
if (now == 0) {
return new vec2d(0,0)
} else {
return this.scale(e/now)
}
} else {
return Math.sqrt(this.dot(this))
}
}
rot(phi) { // rotate the vector by angle phi
if (typeof(phi)!="number" || isNaN(phi)) throw "rot(phi) : phi must be a number";
let c = Math.cos(phi);
let s = Math.sin(phi);
let new_x = this._x * c + this._y * s;
let new_y = -this._x * s + this._y * c;
return new this.constructor( new_x, new_y);
}
turnr() {
return new this.constructor( -this._y, this._x);
}
turnl() {
return new this.constructor( this._y, -this._x);
}
unit() {
return this.scale(1/this.len());
}
norm(sgn) {
return (sgn ? this.unit().turnl() : this.unit().turnr() );
}
phi() {
// so that (1,0)->0, (0,-1)->PI/2, (-1,0)->PI, (0,1)->3*PI/2
return (this._x == 0 && this._y==0) ? NaN : (Math.PI + Math.atan2( this._y, -this._x))%(2*Math.PI);
}
static SUM(vectors) {
let a = ((vectors instanceof Array) ? vectors : Array.from(arguments));
let res
try {
res = a.reduce((prev,curr)=>prev.add(curr));
} catch {
throw "vec2d.SUM : all elements must be vec2d"
}
return res
}
}
Math.atan2(-0.000001,-1)
v1 = new vec2d(1, 0)
v2 = new vec2d(2,2)
v1.add(v2)
v1.sub(v2)
v1.scale(3).add(v1.scale(-1))
v2.len()
v2.len(3)
v2.len(3).len() // ~3
new vec2d(1, 0).phi()
new vec2d(0, -1).phi() // pi/2
new vec2d(-1, 0).phi() // pi
new vec2d(0, 1).phi() // pi*3/2
new vec2d(1,-1).turnl()
new vec2d(1,0).rot(-Math.PI*0.75)
new vec2d(1,1).phi()
v2.unit()
v2.norm()
v2.norm().turnr()
v2.norm().turnl()
md`### dot product and cross-product`
v2.dot(v1)
v2.xprod(v1)
new vec2d(1,0).dot(new vec2d(0,1)) // othogonal vectors
new vec2d(1,0).xprod(new vec2d(0,1)) // othogonal
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