math/big: rename (*Float).Format to (*Float).Text

This paves the way for a fmt-compatible (*Float).Format method.
A better name then Text is still desirable (suggestions welcome).

This is partly fixing issue #10938.

Change-Id: I59c20a8cee11f5dba059fe0f38b414fe75f2ab13
Reviewed-on: https://go-review.googlesource.com/10493
Reviewed-by: Alan Donovan <adonovan@google.com>
diff --git a/src/math/big/bits_test.go b/src/math/big/bits_test.go
index 14ecab5..985b60b 100644
--- a/src/math/big/bits_test.go
+++ b/src/math/big/bits_test.go
@@ -217,7 +217,7 @@
 		{append(Bits{2, 1, 0} /* 7 */, Bits{3, 1} /* 10 */ ...), "0x.88p+5" /* 17 */},
 	} {
 		f := test.bits.Float()
-		if got := f.Format('p', 0); got != test.want {
+		if got := f.Text('p', 0); got != test.want {
 			t.Errorf("setBits(%v) = %s; want %s", test.bits, got, test.want)
 		}
 	}
diff --git a/src/math/big/float.go b/src/math/big/float.go
index 1563528..dff4054 100644
--- a/src/math/big/float.go
+++ b/src/math/big/float.go
@@ -363,7 +363,7 @@
 	}
 	const msb = 1 << (_W - 1)
 	if x.mant[m-1]&msb == 0 {
-		panic(fmt.Sprintf("msb not set in last word %#x of %s", x.mant[m-1], x.Format('p', 0)))
+		panic(fmt.Sprintf("msb not set in last word %#x of %s", x.mant[m-1], x.Text('p', 0)))
 	}
 	if x.prec == 0 {
 		panic("zero precision finite number")
diff --git a/src/math/big/float_test.go b/src/math/big/float_test.go
index 7df9fc7..23abe18 100644
--- a/src/math/big/float_test.go
+++ b/src/math/big/float_test.go
@@ -18,7 +18,7 @@
 func (x *Float) uint64() uint64 {
 	u, acc := x.Uint64()
 	if acc != Exact {
-		panic(fmt.Sprintf("%s is not a uint64", x.Format('g', 10)))
+		panic(fmt.Sprintf("%s is not a uint64", x.Text('g', 10)))
 	}
 	return u
 }
@@ -26,7 +26,7 @@
 func (x *Float) int64() int64 {
 	i, acc := x.Int64()
 	if acc != Exact {
-		panic(fmt.Sprintf("%s is not an int64", x.Format('g', 10)))
+		panic(fmt.Sprintf("%s is not an int64", x.Text('g', 10)))
 	}
 	return i
 }
@@ -34,7 +34,7 @@
 func TestFloatZeroValue(t *testing.T) {
 	// zero (uninitialized) value is a ready-to-use 0.0
 	var x Float
-	if s := x.Format('f', 1); s != "0.0" {
+	if s := x.Text('f', 1); s != "0.0" {
 		t.Errorf("zero value = %s; want 0.0", s)
 	}
 
@@ -236,7 +236,7 @@
 		m := new(Float)
 		e := x.MantExp(m)
 		if !alike(m, mant) || e != test.exp {
-			t.Errorf("%s.MantExp() = %s, %d; want %s, %d", test.x, m.Format('g', 10), e, test.mant, test.exp)
+			t.Errorf("%s.MantExp() = %s, %d; want %s, %d", test.x, m.Text('g', 10), e, test.mant, test.exp)
 		}
 	}
 }
@@ -247,7 +247,7 @@
 		t.Fatalf("Float.MantExp aliasing error: got %d; want 10", e)
 	}
 	if want := makeFloat("0.5"); !alike(x, want) {
-		t.Fatalf("Float.MantExp aliasing error: got %s; want %s", x.Format('g', 10), want.Format('g', 10))
+		t.Fatalf("Float.MantExp aliasing error: got %s; want %s", x.Text('g', 10), want.Text('g', 10))
 	}
 }
 
@@ -279,12 +279,12 @@
 		var z Float
 		z.SetMantExp(frac, test.exp)
 		if !alike(&z, want) {
-			t.Errorf("SetMantExp(%s, %d) = %s; want %s", test.frac, test.exp, z.Format('g', 10), test.z)
+			t.Errorf("SetMantExp(%s, %d) = %s; want %s", test.frac, test.exp, z.Text('g', 10), test.z)
 		}
 		// test inverse property
 		mant := new(Float)
 		if z.SetMantExp(mant, want.MantExp(mant)).Cmp(want) != 0 {
-			t.Errorf("Inverse property not satisfied: got %s; want %s", z.Format('g', 10), test.z)
+			t.Errorf("Inverse property not satisfied: got %s; want %s", z.Text('g', 10), test.z)
 		}
 	}
 }
@@ -562,7 +562,7 @@
 		var f Float
 		f.SetUint64(want)
 		if got := f.uint64(); got != want {
-			t.Errorf("got %#x (%s); want %#x", got, f.Format('p', 0), want)
+			t.Errorf("got %#x (%s); want %#x", got, f.Text('p', 0), want)
 		}
 	}
 
@@ -573,7 +573,7 @@
 		got := f.uint64()
 		want := x &^ (1<<(64-prec) - 1) // cut off (round to zero) low 64-prec bits
 		if got != want {
-			t.Errorf("got %#x (%s); want %#x", got, f.Format('p', 0), want)
+			t.Errorf("got %#x (%s); want %#x", got, f.Text('p', 0), want)
 		}
 	}
 }
@@ -596,7 +596,7 @@
 			var f Float
 			f.SetInt64(want)
 			if got := f.int64(); got != want {
-				t.Errorf("got %#x (%s); want %#x", got, f.Format('p', 0), want)
+				t.Errorf("got %#x (%s); want %#x", got, f.Text('p', 0), want)
 			}
 		}
 	}
@@ -608,7 +608,7 @@
 		got := f.int64()
 		want := x &^ (1<<(63-prec) - 1) // cut off (round to zero) low 63-prec bits
 		if got != want {
-			t.Errorf("got %#x (%s); want %#x", got, f.Format('p', 0), want)
+			t.Errorf("got %#x (%s); want %#x", got, f.Text('p', 0), want)
 		}
 	}
 }
@@ -639,7 +639,7 @@
 			var f Float
 			f.SetFloat64(want)
 			if got, acc := f.Float64(); got != want || acc != Exact {
-				t.Errorf("got %g (%s, %s); want %g (Exact)", got, f.Format('p', 0), acc, want)
+				t.Errorf("got %g (%s, %s); want %g (Exact)", got, f.Text('p', 0), acc, want)
 			}
 		}
 	}
@@ -651,7 +651,7 @@
 		got, _ := f.Float64()
 		want := float64(x &^ (1<<(52-prec) - 1)) // cut off (round to zero) low 53-prec bits
 		if got != want {
-			t.Errorf("got %g (%s); want %g", got, f.Format('p', 0), want)
+			t.Errorf("got %g (%s); want %g", got, f.Text('p', 0), want)
 		}
 	}
 
@@ -664,7 +664,7 @@
 	var f Float
 	f.SetFloat64(math.NaN())
 	// should not reach here
-	t.Errorf("got %s; want ErrNaN panic", f.Format('p', 0))
+	t.Errorf("got %s; want ErrNaN panic", f.Text('p', 0))
 }
 
 func TestFloatSetInt(t *testing.T) {
@@ -696,9 +696,9 @@
 		}
 
 		// check value
-		got := f.Format('g', 100)
+		got := f.Text('g', 100)
 		if got != want {
-			t.Errorf("got %s (%s); want %s", got, f.Format('p', 0), want)
+			t.Errorf("got %s (%s); want %s", got, f.Text('p', 0), want)
 		}
 	}
 
@@ -738,9 +738,9 @@
 			t.Errorf("got prec = %d; want %d", prec, n)
 		}
 
-		got := f2.Format('g', 100)
+		got := f2.Text('g', 100)
 		if got != want {
-			t.Errorf("got %s (%s); want %s", got, f2.Format('p', 0), want)
+			t.Errorf("got %s (%s); want %s", got, f2.Text('p', 0), want)
 		}
 	}
 }
@@ -1096,13 +1096,13 @@
 		p := makeFloat(test)
 		a := new(Float).Abs(p)
 		if !alike(a, p) {
-			t.Errorf("%s: got %s; want %s", test, a.Format('g', 10), test)
+			t.Errorf("%s: got %s; want %s", test, a.Text('g', 10), test)
 		}
 
 		n := makeFloat("-" + test)
 		a.Abs(n)
 		if !alike(a, p) {
-			t.Errorf("-%s: got %s; want %s", test, a.Format('g', 10), test)
+			t.Errorf("-%s: got %s; want %s", test, a.Text('g', 10), test)
 		}
 	}
 }
@@ -1122,10 +1122,10 @@
 		n2 := new(Float).Neg(p1)
 		p2 := new(Float).Neg(n2)
 		if !alike(n2, n1) {
-			t.Errorf("%s: got %s; want %s", test, n2.Format('g', 10), n1.Format('g', 10))
+			t.Errorf("%s: got %s; want %s", test, n2.Text('g', 10), n1.Text('g', 10))
 		}
 		if !alike(p2, p1) {
-			t.Errorf("%s: got %s; want %s", test, p2.Format('g', 10), p1.Format('g', 10))
+			t.Errorf("%s: got %s; want %s", test, p2.Text('g', 10), p1.Text('g', 10))
 		}
 	}
 }
@@ -1467,7 +1467,7 @@
 
 					cc, acc := C.Float64()
 					if cc != c {
-						t.Errorf("%g/%g = %s; want %.5g\n", a, b, C.Format('g', 5), c)
+						t.Errorf("%g/%g = %s; want %.5g\n", a, b, C.Text('g', 5), c)
 						continue
 					}
 					if acc != Exact {
@@ -1608,10 +1608,10 @@
 		default:
 			panic("unreachable")
 		}
-		if got := z.Format('p', 0); got != test.want || z.Acc() != test.acc {
+		if got := z.Text('p', 0); got != test.want || z.Acc() != test.acc {
 			t.Errorf(
 				"prec = %d (%s): %s %c %s = %s (%s); want %s (%s)",
-				test.prec, test.mode, x.Format('p', 0), test.op, y.Format('p', 0), got, z.Acc(), test.want, test.acc,
+				test.prec, test.mode, x.Text('p', 0), test.op, y.Text('p', 0), got, z.Acc(), test.want, test.acc,
 			)
 		}
 	}
diff --git a/src/math/big/floatconv_test.go b/src/math/big/floatconv_test.go
index 9fc2b89..fffcd70 100644
--- a/src/math/big/floatconv_test.go
+++ b/src/math/big/floatconv_test.go
@@ -113,7 +113,7 @@
 	above1e23 = 100000000000000008388608
 )
 
-func TestFloat64Format(t *testing.T) {
+func TestFloat64Text(t *testing.T) {
 	for _, test := range []struct {
 		x      float64
 		format byte
@@ -257,7 +257,7 @@
 		// {383260575764816448, 'g', -1, "3.8326057576481645e+17"},
 	} {
 		f := new(Float).SetFloat64(test.x)
-		got := f.Format(test.format, test.prec)
+		got := f.Text(test.format, test.prec)
 		if got != test.want {
 			t.Errorf("%v: got %s; want %s", test, got, test.want)
 		}
@@ -277,7 +277,7 @@
 	}
 }
 
-func TestFloatFormat(t *testing.T) {
+func TestFloatText(t *testing.T) {
 	for _, test := range []struct {
 		x      string
 		prec   uint
@@ -378,7 +378,7 @@
 			continue
 		}
 
-		got := f.Format(test.format, test.digits)
+		got := f.Text(test.format, test.digits)
 		if got != test.want {
 			t.Errorf("%v: got %s; want %s", test, got, test.want)
 		}
diff --git a/src/math/big/floatexample_test.go b/src/math/big/floatexample_test.go
index d9d39ed..d9662fc 100644
--- a/src/math/big/floatexample_test.go
+++ b/src/math/big/floatexample_test.go
@@ -17,9 +17,9 @@
 	y.SetFloat64(2.718281828) // y is automatically set to 53bit precision
 	z.SetPrec(32)
 	z.Add(&x, &y)
-	fmt.Printf("x = %s (%s, prec = %d, acc = %s)\n", &x, x.Format('p', 0), x.Prec(), x.Acc())
-	fmt.Printf("y = %s (%s, prec = %d, acc = %s)\n", &y, y.Format('p', 0), y.Prec(), y.Acc())
-	fmt.Printf("z = %s (%s, prec = %d, acc = %s)\n", &z, z.Format('p', 0), z.Prec(), z.Acc())
+	fmt.Printf("x = %s (%s, prec = %d, acc = %s)\n", &x, x.Text('p', 0), x.Prec(), x.Acc())
+	fmt.Printf("y = %s (%s, prec = %d, acc = %s)\n", &y, y.Text('p', 0), y.Prec(), y.Acc())
+	fmt.Printf("z = %s (%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)
diff --git a/src/math/big/ftoa.go b/src/math/big/ftoa.go
index 4c3e743..502e6fd 100644
--- a/src/math/big/ftoa.go
+++ b/src/math/big/ftoa.go
@@ -13,8 +13,8 @@
 	"strings"
 )
 
-// Format converts the floating-point number x to a string according
-// to the given format and precision prec. The format is one of:
+// Text converts the floating-point number x to a string according
+// to the given format and precision prec. The format must be one of:
 //
 //	'e'	-d.dddde±dd, decimal exponent, at least two (possibly 0) exponent digits
 //	'E'	-d.ddddE±dd, decimal exponent, at least two (possibly 0) exponent digits
@@ -37,20 +37,18 @@
 // The prec value is ignored for the 'b' or 'p' format.
 //
 // BUG(gri) Float.Format does not accept negative precisions.
-// BUG(gri) The Float.Format signature conflicts with Format(f fmt.State, c rune).
-//          (https://github.com/golang/go/issues/10938)
-func (x *Float) Format(format byte, prec int) string {
+func (x *Float) Text(format byte, prec int) string {
 	const extra = 10 // TODO(gri) determine a good/better value here
 	return string(x.Append(make([]byte, 0, prec+extra), format, prec))
 }
 
-// String formats x like x.Format('g', 10).
+// String formats x like x.Text('g', 10).
 func (x *Float) String() string {
-	return x.Format('g', 10)
+	return x.Text('g', 10)
 }
 
 // Append appends to buf the string form of the floating-point number x,
-// as generated by x.Format, and returns the extended buffer.
+// as generated by x.Text, and returns the extended buffer.
 func (x *Float) Append(buf []byte, fmt byte, prec int) []byte {
 	// sign
 	if x.neg {