// limit how deep a structure we generate.
	var n int
	defer func() { p.nestLev -= n }()
	for n = 1; ; n++ {
		incNestLev(p)
		op, oprec := p.tokPrec()
		if oprec < prec1 {
			return x
		}
		pos := p.expect(op)
		y := p.parseBinaryExpr(nil, oprec+1)
		x = &ast.BinaryExpr{X: x, OpPos: pos, Op: op, Y: y}
	}
}

// The result may be a type or even a raw type ([...]int).

		n := n.(*BinaryExpr)
		exprFmt(n.X, s, nprec)
		fmt.Fprintf(s, " %v ", n.Op())
		exprFmt(n.Y, s, nprec+1)

	case OANDAND,
		OOROR:
		n := n.(*LogicalExpr)
		exprFmt(n.X, s, nprec)
		fmt.Fprintf(s, " %v ", n.Op())
		exprFmt(n.Y, s, nprec+1)

	case OSEND:
		n := n.(*SendStmt)
		exprFmt(n.Chan, s, nprec)
		fmt.Fprintf(s, " <- ")
		exprFmt(n.Value, s, nprec+1)

	case OADDSTR:

		eprec := prec
		if eprec > len(d.mant) && len(d.mant) >= d.exp {
			eprec = len(d.mant)
		}
		// %e is used if the exponent from the conversion
		// is less than -4 or greater than or equal to the precision.
		// If precision was the shortest possible, use eprec = 6 for
		// this decision.
		if shortest {
			eprec = 6
		}
		exp := d.exp - 1
		if exp < -4 || exp >= eprec {
			if prec > len(d.mant) {

			eprec = 6
		}
		exp := digs.dp - 1
		if exp < -4 || exp >= eprec {
			if prec > digs.nd {
				prec = digs.nd
			}
			return fmtE(dst, neg, digs, prec-1, fmt+'e'-'g')
		}
		if prec > digs.dp {
			prec = digs.nd
		}
		return fmtF(dst, neg, digs, max(prec-digs.dp, 0))
	}

	// unknown format
	return append(dst, '%', fmt)
}

	} {
		x := makeFloat(test.x).SetPrec(test.prec)
		prec := test.prec
		if prec > MaxPrec {
			prec = MaxPrec
		}
		if got := x.Prec(); got != prec {
			t.Errorf("%s.SetPrec(%d).Prec() == %d; want %d", test.x, test.prec, got, prec)
		}
		if got, acc := x.String(), x.Acc(); got != test.want || acc != test.acc {
			t.Errorf("%s.SetPrec(%d) = %s (%s); want %s (%s)", test.x, test.prec, got, acc, test.want, test.acc)
		}
	}
}

		u.prec = t.prec
		v.prec = t.prec
		u.Mul(t, t)     // u = t²
		u.Mul(x, u)     //   = xt²
		v.Sub(three, u) // v = 3 - xt²
		u.Mul(t, v)     // u = t(3 - xt²)
		u.exp--         //   = ½t(3 - xt²)
		return t.Set(u)
	}

	xf, _ := x.Float64()
	sqi := newFloat(z.prec)
	sqi.SetFloat64(1 / math.Sqrt(xf))
	for prec := z.prec + 32; sqi.prec < prec; {
		sqi.prec *= 2
		sqi = ng(sqi)
	}
	// sqi = 1/√x

		}
		if ps.llvmStyle {
			skipParens = true
		}
	}

	if skipParens {
		ps.print(left)
	} else if ps.llvmStyle {
		prec := precPrimary
		if p, ok := left.(hasPrec); ok {
			prec = p.prec()
		}
		needsParen := false
		if prec > b.prec() {
			needsParen = true
		}
		if needsParen {
			ps.startScope('(')
		}

		ps.print(left)

		if needsParen {

				s.tok = _Semi
				break
			}
			goto redo
		}
		s.op, s.prec = Div, precMul
		goto assignop

	case '%':
		s.nextch()
		s.op, s.prec = Rem, precMul
		goto assignop

	case '&':
		s.nextch()
		if s.ch == '&' {
			s.nextch()
			s.op, s.prec = AndAnd, precAndAnd
			s.tok = _Operator
			break
		}
		s.op, s.prec = And, precMul
		if s.ch == '^' {
			s.nextch()
			s.op = AndNot

type testState struct {
	width   int
	widthOK bool
	prec    int
	precOK  bool
	flag    map[int]bool
}

var _ fmt.State = testState{}

func (s testState) Write(b []byte) (n int, err error) {
	panic("unimplemented")
}

func (s testState) Width() (wid int, ok bool) {
	return s.width, s.widthOK
}

func (s testState) Precision() (prec int, ok bool) {
	return s.prec, s.precOK
}

	z.Add(&x, &y)
	fmt.Printf("x = %.10g (%s, prec = %d, acc = %s)\n", &x, x.Text('p', 0), x.Prec(), x.Acc())
	fmt.Printf("y = %.10g (%s, prec = %d, acc = %s)\n", &y, y.Text('p', 0), y.Prec(), y.Acc())
	fmt.Printf("z = %.10g (%s, prec = %d, acc = %s)\n", &z, z.Text('p', 0), z.Prec(), z.Acc())
	// Output:
	// x = 1000 (0x.fap+10, prec = 64, acc = Exact)
	// y = 2.718281828 (0x.adf85458248cd8p+2, prec = 53, acc = Exact)