t.tok = ROT
			return ROT
		}
	case '<':
		if s.Peek() == '<' {
			s.Next()
			t.tok = LSH
			return LSH
		}
	case '>':
		if s.Peek() == '>' {
			s.Next()
			t.tok = RSH
			return RSH
		}
	}
	return t.tok
}

func (t *Tokenizer) Close() {
	if t.file != nil {
		t.file.Close()
	}

}

// Lsh sets z = x << s and returns z.
func (z *Int) Lsh(x *Int, s uint) *Int {
	x.doinit()
	z.doinit()
	C._mpz_mul_2exp(&z.i[0], &x.i[0], C.ulong(s))
	return z
}

// Rsh sets z = x >> s and returns z.
func (z *Int) Rsh(x *Int, s uint) *Int {
	x.doinit()
	z.doinit()
	C._mpz_div_2exp(&z.i[0], &x.i[0], C.ulong(s))
	return z
}

// Exp sets z = x^y % m and returns z.
// If m == nil, Exp sets z = x^y.

type ScanToken rune

const (
	// Asm defines some two-character lexemes. We make up
	// a rune/ScanToken value for them - ugly but simple.
	LSH          ScanToken = -1000 - iota // << Left shift.
	RSH                                   // >> Logical right shift.
	ARR                                   // -> Used on ARM for shift type 3, arithmetic right shift.

	//	">>" == 1
	//	"->" == 2
	//	"@>" == 3
	r1, ok := p.registerReference(name)
	if !ok {
		return 0
	}
	var op int16
	switch p.next().ScanToken {
	case lex.LSH:
		op = 0
	case lex.RSH:
		op = 1
	case lex.ARR:
		op = 2
	case lex.ROT:
		// following instructions on ARM64 support rotate right
		// AND, ANDS, TST, BIC, BICS, EON, EOR, ORR, MVN, ORN
		op = 3
	}
	tok := p.next()