if len(strs) == 1 {
		return xfix
	}
	// compare first to rest
	for _, str := range strs[1:] {
		xfixl := len(xfix)
		strl := len(str)
		// short-circuit empty strings
		if xfixl == 0 || strl == 0 {
			return ""
		}
		// maximum possible length
		maxl := min(strl, xfixl)
		// compare letters
		if pre {
			// prefix, iterate left to right
			for i := range maxl {
				if xfix[i] != str[i] {

	BTRW R11, R11                           // 66450fb3db
	BTRL $7, (BX)                           // 0fba3307
	BTRL $7, (R11)                          // 410fba3307
	BTRL $7, DX                             // 0fbaf207
	BTRL $7, R11                            // 410fbaf307
	BTRL DX, (BX)                           // 0fb313
	BTRL R11, (BX)                          // 440fb31b
	BTRL DX, (R11)                          // 410fb313

    an alternative to accepting a `callable` loss.
*   Adds `beta` hyperparameter to
    [FTRL](https://www.tensorflow.org/api_docs/python/tf/keras/optimizers/Ftrl)
    optimizer classes (Keras and others) to match
    [FTRL paper](https://research.google.com/pubs/archive/41159.pdf).
*   `Optimizer.__init__` now accepts a `gradient_aggregator` to allow for