✨ feat(Integer): Implement valueOf.

Author: make-github-pseudonymous-again

src/Integer.js

@@ -8,6 +8,8 @@ import {
 	increment ,
 } from '@aureooms/js-integer-big-endian' ;
 
+import { MIN_NUMBER , MAX_NUMBER , MAX_BASE } from './_limits' ;
+
 export class Integer {
 
 	constructor ( base , is_negative , limbs ) {
@@ -369,4 +371,24 @@ export class Integer {
 		return this.cmp( other ) !== 0 ;
 	}
 
+	valueOf ( ) {
+
+		if (this.gtn(MAX_NUMBER)) throw new ValueError(`Cannot call valueOf on Integer larger than ${MAX_NUMBER}. Got ${this.toString()}`) ;
+		if (this.ltn(MIN_NUMBER)) throw new ValueError(`Cannot call valueOf on Integer smaller than ${MIN_NUMBER}. Got ${this.toString()}`) ;
+
+		const limbs = convert( this.base , MAX_BASE , this.limbs , 0 , this.limbs.length ) ;
+
+		const sign = this.is_negative ? -1 : 1 ;
+
+		const value = limbs.length === 2 ?
+			limbs[0] * MAX_BASE + limbs[1] :
+			limbs[0] ;
+
+		return sign * value ;
+	}
+
+	toNumber ( ) {
+		return this.valueOf( ) ;
+	}
+
 }

src/_limits.js

@@ -0,0 +1,5 @@
+// The range of valid numbers is -2^53 to 2^53 - 1
+export const MAX_NUMBER = Math.pow(2,53) - 1 ;
+export const MIN_NUMBER = -Math.pow(2,53) ;
+export const MIN_BASE = 2 ;
+export const MAX_BASE = Math.ceil(Math.sqrt(Math.pow(2,53))) ;

test/src/Integer/toNumber.js

@@ -0,0 +1,45 @@
+import test from 'ava' ;
+
+import { randint } from '@aureooms/js-random' ;
+import { ValueError } from '@aureooms/js-error' ;
+
+import { ZZ , MIN_NUMBER , MAX_NUMBER } from '../../../src' ;
+
+function macro ( t , number ) {
+	const integer = ZZ.from(number) ;
+	t.is(number.toString(), integer.toString());
+	t.is(number, integer.toNumber());
+}
+
+macro.title = ( providedTitle , number ) => `toNumber: ${number}` ;
+
+function throws ( t , string ) {
+	const integer = ZZ.from(string) ;
+	t.is(string, integer.toString()) ;
+	t.throws(() => integer.toNumber(), { instanceOf: ValueError }) ;
+}
+
+throws.title = ( providedTitle , string ) => `toNumber: ${string} throws` ;
+
+const tested = new Set() ;
+const N = 100 ;
+
+const once = x => {
+	tested.add(x) ;
+	test( macro , x ) ;
+}
+
+once(0);
+once(1);
+once(-1);
+once(MIN_NUMBER);
+once(MAX_NUMBER);
+
+while ( tested.size < N ) {
+	const number = randint(MIN_NUMBER, MAX_NUMBER + 1) ;
+	if ( tested.has(number) ) continue ;
+	once(number) ;
+}
+
+test( throws , '9007199254740992' ) ;
+test( throws , '-9007199254740993' ) ;