function _broadcastReplacement (replacement, index) {
    if (typeof replacement === 'string') {
      throw new Error('can\'t boradcast a string')
    }
    if (index._isScalar) {
      return replacement
    }

    const indexSize = index.size()
    if (indexSize.every(d => d > 0)) {
      try {
        return add(replacement, zeros(indexSize))
      } catch (error) {
        return replacement
      }
    } else {
      return replacement
    }
  }
Broadcasts a replacment value to be the same size as index
@param {number | BigNumber | Array | Matrix} replacement Replacement value to try to broadcast
@param {*} index Index value
@returns broadcasted replacement that matches the size of index