quaeratin/node/double-representation/bit-length.js

An extended precision floating point library (as per Shewchuk) - precision only limited by overflow / underflow

import { getLowestSetBit, getHighestSetBit } from "./get-max-set-bit.js";
import { eCompress } from "../double-expansion/e-compress.js";
import { exponent } from "./exponent.js";
import { eSign } from "../double-expansion/e-sign.js";
/**
 * Returns the bit-length of the significand of the given number in such a way
 * that trailing zeros are not counted.
 * @param a A double precision floating point number
 */
function bitLength(a) {
    if (a === 0) {
        return 0;
    }
    return getHighestSetBit(a) - getLowestSetBit(a) + 1;
}
/**
 * Returns the bit-length of the significand of the given floating point
 * expansion in such a way that trailing zeros are not counted.
 * * precondition: subnormals not currently supported
 * @param a A double precision floating point expansion
 */
function expBitLength(a) {
    const a_ = eCompress(a);
    if (eSign(a_) === 0) {
        return 0;
    }
    const msbyte = a_[a_.length - 1];
    const lsbyte = a_[0];
    return exponent(msbyte) - exponent(lsbyte) + (53 - getLowestSetBit(lsbyte));
}
export { bitLength, expBitLength };
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