Construct float from sign, exponent, significand ints

float64.js

function constructFloat64(sign, exp, sig) {
  // Constants
  const EXPONENT_BIAS = 1023n;
  const EXPONENT_MASK = 0x7FFn;
  const SIGNIFICAND_MASK = 0xFFFFFFFFFFFFFn;

  console.log(sign, exp, sig, BigInt(sig) & SIGNIFICAND_MASK)
  // Mask and adjust the components
  sign = sign < 0 ? 1n : 0n;
  exp = (BigInt(exp) + EXPONENT_BIAS) & EXPONENT_MASK;  // Apply bias and mask to 11 bits
  sig = BigInt(sig) & SIGNIFICAND_MASK;  // Mask to 52 bits


  // Combine the parts into a 64-bit value
  const bits = (sign << 63n) | (exp << 52n) | sig;

  // Convert the 64-bit value to a Float64Array
  const buffer = new ArrayBuffer(8);
  const view = new DataView(buffer);
  view.setBigUint64(0, bits);

  // Return the float value
  return view.getFloat64(0);
}