🎨 style: Assert some documentated assumptions.

⚠️ Some of the added assertions call the measure method which
causes a cascade of measure caching behaviour. This may cause problems
when removing the assertion for optimized runtime. In general, I should
find an elegant way to test with and without the assertions.

Author: make-github-pseudonymous-again

src/1-digit/1-One.js

@@ -2,6 +2,8 @@ import {Digit, Two, Three} from '.';
 import {node2, node3} from '../2-node';
 import {Split} from '../0-core';
 
+import assert from 'assert';
+
 export function One(a) {
 	this.a = a;
 	this.v = null;
@@ -43,9 +45,10 @@ One.prototype.node = function (M) {
 };
 
 /**
- * It is assumed that p(|this|) is true.
+ * It is assumed that p(i+|this|) is true.
  */
 One.prototype.splitDigit = function (p, i, M) {
+	assert(p(M.plus(i, this.measure(M)))); // /!\ Potential Heisenbug generator.
 	return new Split([], this.a, []);
 };
 
@@ -54,6 +57,7 @@ One.prototype._nodes = function (M, other) {
 	if (other instanceof Two) return [node3(M, this.a, other.a, other.b)];
 	if (other instanceof Three)
 		return [node2(M, this.a, other.a), node2(M, other.b, other.c)];
+	assert(other instanceof Digit);
 	return [node3(M, this.a, other.a, other.b), node2(M, other.c, other.d)];
 };
 

src/1-digit/2-Two.js

@@ -2,6 +2,8 @@ import {Digit, One, Three} from '.';
 import {node2, node3} from '../2-node';
 import {Split} from '../0-core';
 
+import assert from 'assert';
+
 export function Two(a, b) {
 	this.a = a;
 	this.b = b;
@@ -46,9 +48,10 @@ Two.prototype.node = function (M) {
 };
 
 /**
- * It is assumed that p(|this|) is true.
+ * It is assumed that p(i+|this|) is true.
  */
 Two.prototype.splitDigit = function (p, i, M) {
+	assert(p(M.plus(i, this.measure(M)))); // /!\ Potential Heisenbug generator.
 	i = M.plus(i, M.measure(this.a));
 	if (p(i)) return new Split([], this.a, [this.b]);
 	return new Split([this.a], this.b, []);
@@ -60,6 +63,7 @@ Two.prototype._nodes = function (M, other) {
 		return [node2(M, this.a, this.b), node2(M, other.a, other.b)];
 	if (other instanceof Three)
 		return [node3(M, this.a, this.b, other.a), node2(M, other.b, other.c)];
+	assert(other instanceof Digit);
 	return [
 		node3(M, this.a, this.b, other.a),
 		node3(M, other.b, other.c, other.d)

src/1-digit/3-Three.js

@@ -2,6 +2,8 @@ import {Digit, One, Two, Four} from '.';
 import {node2, node3} from '../2-node';
 import {Split} from '../0-core';
 
+import assert from 'assert';
+
 export function Three(a, b, c) {
 	this.a = a;
 	this.b = b;
@@ -49,9 +51,10 @@ Three.prototype.node = function (M) {
 };
 
 /**
- * It is assumed that p(|this|) is true.
+ * It is assumed that p(i+|this|) is true.
  */
 Three.prototype.splitDigit = function (p, i, M) {
+	assert(p(M.plus(i, this.measure(M)))); // /!\ Potential Heisenbug generator.
 	i = M.plus(i, M.measure(this.a));
 	if (p(i)) return new Split([], this.a, [this.b, this.c]);
 	i = M.plus(i, M.measure(this.b));
@@ -69,6 +72,7 @@ Three.prototype._nodes = function (M, other) {
 			node3(M, this.a, this.b, this.c),
 			node3(M, other.a, other.b, other.c)
 		];
+	assert(other instanceof Four);
 	return [
 		node3(M, this.a, this.b, this.c),
 		node2(M, other.a, other.b),

src/1-digit/4-Four.js

@@ -2,6 +2,8 @@ import {Digit, One, Two, Three} from '.';
 import {node2, node3} from '../2-node';
 import {Split} from '../0-core';
 
+import assert from 'assert';
+
 export function Four(a, b, c, d) {
 	this.a = a;
 	this.b = b;
@@ -50,9 +52,10 @@ Four.prototype.node = function (M) {
 };
 
 /**
- * It is assumed that p(|this|) is true.
+ * It is assumed that p(i+|this|) is true.
  */
 Four.prototype.splitDigit = function (p, i, M) {
+	assert(p(M.plus(i, this.measure(M)))); // /!\ Potential Heisenbug generator.
 	i = M.plus(i, M.measure(this.a));
 	if (p(i)) return new Split([], this.a, [this.b, this.c, this.d]);
 	i = M.plus(i, M.measure(this.b));
@@ -76,6 +79,7 @@ Four.prototype._nodes = function (M, other) {
 			node2(M, this.d, other.a),
 			node2(M, other.b, other.c)
 		];
+	assert(other instanceof Four);
 	return [
 		node3(M, this.a, this.b, this.c),
 		node3(M, this.d, other.a, other.b),

src/3-tree/implementations/2-Deep.js

@@ -121,9 +121,11 @@ Deep.prototype[Symbol.iterator] = function* () {
 };
 
 /**
- * It is assumed that p(|this|) is true.
+ * It is assumed that p(i+|this|) is true.
  */
 Deep.prototype.splitTree = function (p, i) {
+	assert(p(this.M.plus(i, this.measure())));
+
 	const {left, middle, right, M} = this;
 
 	// See if the split point is inside the left tree