code: function consumeBackward(stream) {
  	const start = stream.pos;
  	let ch, hadDot = false, hadNumber = false;
  	// NB a StreamReader insance can be editor-specific and contain objects
  	// as a position marker. Since we don’t know for sure how to compare editor
  	// position markers, use consumed length instead to detect if number was consumed
  	let len = 0;
  
  	while (!isSoF(stream)) {
  		stream.backUp(1);
  		ch = stream.peek();
  
  		if (ch === DOT && !hadDot && hadNumber) {
  			hadDot = true;
  		} else if (!isNumber(ch)) {
  			stream.next();
  			break;
  		}
  
  		hadNumber = true;
  		len++;
  	}
  
  	if (len) {
  		const pos = stream.pos;
  		stream.start = pos;
  		stream.pos = start;
  		return true;
  	}
  
  	stream.pos = start;
  	return false;
  }
docs: Consumes number in backward stream direction
  @param  {StreamReader} stream
  @return {Boolean}        Returns true if number was consumed