Xah Talk Show 2019-12-14 hand writing Chinese, JavaScript coding vector dot product function style, intro to constructed language

topic talked:

• Drawing Tablet Drawing Tablet
• Logitech G502 Mouse Logitech G502 Mouse
• 常用汉字 Most Used Chinese Chars
• Chinese Characters Drum Keyboard
• Intro to Chinese Punctuation
• Drawing Tablet
• JavaScript, code function for dot product of vector of any dimension, function programing style
• JS: Function Rest Parameters
• Intro to Constructed Languages
• linguistics. flammable vs inflammable, active vs inactive, do vs undo vs understand, quasi pseudo semi.
• Volapük, Esperanto, Modern Hebrew

xah_talk_show_2019-12-14.txt

// we are going to write a bunch of functions that does matrix and vector multiplication
// and these functions will work in any dimensions

const cos = Math.cos;
const sin = Math.sin;
const π = Math.PI;

// dot([a,b,c], [x,y,z] );
// this is what dot product means
// is a*x + b*y + c*z

// dot product of 2 vectors, vector must be 2D
const f_vec_dot_2d = ([a1, a2], [b1, b2]) => (a1 * b1 + a2 * b2);

// dot product of 3 vectors, vector must be 3D
const f_vec_dot_3d = ([a1, a2, a3], [b1, b2, b3]) => (a1 * b1 + a2 * b2 + a3 * b3);

// dot product of 2 vectors, vectors can be of any dimension
const f_vec_dot = (...vectors) =>
 vectors.reduce((v1, v2) => v1.map((x, i) => x * v2[i]))
  .reduce((a, b) => (a + b));

const vA = [1, 2];
const vB = [3, 4];
console.assert(f_vec_dot_2d(vA, vB) === 11);
console.assert(f_vec_dot(vA, vB) === 11);

const vC = [1, 2, 3];
const vD = [3, 4, 9];
console.assert(f_vec_dot_3d(vC, vD) === 38);
console.assert(f_vec_dot(vC, vD) === 38);

// vlen2D returns the length of the vector of a 2d vector
const vlen2D = (v) => Math.hypot(...v);

// f_vec_length returns the length of the vector
const f_vec_length = (v) => Math.hypot(...v);