CODEWITHSUNDEEP
javascript
KostasRim
KostasRim

Reputation: 2053

BigInt misbehaving on large numbers

I have two cases where BigInt misbehaves completely.

For completeness I attach the documentation of BigInt BigInt doc and I quote

BigInt.asIntN() Wraps a BigInt value to a signed integer between -2^(width-1) and 2^(width-1 - 1).

BigInt.asUintN() Wraps a BigInt value to an unsigned integer between 0 and 2^(width - 1).

For 64 bit positive integer the max is 9223372036854775808 For 64 bit signed integer the min is -9223372036854775808

Case 1:

const max: BigInt = BigInt.asUintN(64, BigInt(9223372036854775806));
console.log("max is: " + max);

and prints

9223372036854775808 when it should print:
9223372036854775806

why? It works on small numbers like 10, 100 etc but fails on the limit.

Case 2:

const min: BigInt = BigInt.asIntN(64, BigInt(-9223372036854775808));
console.log("bits: " + min.toString(2).length);

and prints:

bits: 65

when clearly according to the documentation it should be 64

Upvotes: 1

Views: 133

Answers (1)

Nina Scholz
Nina Scholz

Reputation: 386512

You could take the number as string for conversion to BigInt.

const max = BigInt.asUintN(64, BigInt('9223372036854775806'));
console.log("max is: " + max);

Upvotes: 2

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