diff options
Diffstat (limited to 'starlark/value.go')
| -rw-r--r-- | starlark/value.go | 100 |
1 files changed, 71 insertions, 29 deletions
diff --git a/starlark/value.go b/starlark/value.go index eb0e84e..8d1b88a 100644 --- a/starlark/value.go +++ b/starlark/value.go @@ -385,10 +385,47 @@ func (x Bool) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error // Float is the type of a Starlark float. type Float float64 -func (f Float) String() string { return strconv.FormatFloat(float64(f), 'g', 6, 64) } -func (f Float) Type() string { return "float" } -func (f Float) Freeze() {} // immutable -func (f Float) Truth() Bool { return f != 0.0 } +func (f Float) String() string { + var buf strings.Builder + f.format(&buf, 'g') + return buf.String() +} + +func (f Float) format(buf *strings.Builder, conv byte) { + ff := float64(f) + if !isFinite(ff) { + if math.IsInf(ff, +1) { + buf.WriteString("+inf") + } else if math.IsInf(ff, -1) { + buf.WriteString("-inf") + } else { + buf.WriteString("nan") + } + return + } + + // %g is the default format used by str. + // It uses the minimum precision to avoid ambiguity, + // and always includes a '.' or an 'e' so that the value + // is self-evidently a float, not an int. + if conv == 'g' || conv == 'G' { + s := strconv.FormatFloat(ff, conv, -1, 64) + buf.WriteString(s) + // Ensure result always has a decimal point if no exponent. + // "123" -> "123.0" + if strings.IndexByte(s, conv-'g'+'e') < 0 && strings.IndexByte(s, '.') < 0 { + buf.WriteString(".0") + } + return + } + + // %[eEfF] use 6-digit precision + buf.WriteString(strconv.FormatFloat(ff, conv, 6, 64)) +} + +func (f Float) Type() string { return "float" } +func (f Float) Freeze() {} // immutable +func (f Float) Truth() Bool { return f != 0.0 } func (f Float) Hash() (uint32, error) { // Equal float and int values must yield the same hash. // TODO(adonovan): opt: if f is non-integral, and thus not equal @@ -409,27 +446,34 @@ func isFinite(f float64) bool { func (x Float) CompareSameType(op syntax.Token, y_ Value, depth int) (bool, error) { y := y_.(Float) - switch op { - case syntax.EQL: - return x == y, nil - case syntax.NEQ: - return x != y, nil - case syntax.LE: - return x <= y, nil - case syntax.LT: - return x < y, nil - case syntax.GE: - return x >= y, nil - case syntax.GT: - return x > y, nil + return threeway(op, floatCmp(x, y)), nil +} + +// floatCmp performs a three-valued comparison on floats, +// which are totally ordered with NaN > +Inf. +func floatCmp(x, y Float) int { + if x > y { + return +1 + } else if x < y { + return -1 + } else if x == y { + return 0 } - panic(op) + + // At least one operand is NaN. + if x == x { + return -1 // y is NaN + } else if y == y { + return +1 // x is NaN + } + return 0 // both NaN } func (f Float) rational() *big.Rat { return new(big.Rat).SetFloat64(float64(f)) } // AsFloat returns the float64 value closest to x. -// The f result is undefined if x is not a float or int. +// The f result is undefined if x is not a float or Int. +// The result may be infinite if x is a very large Int. func AsFloat(x Value) (f float64, ok bool) { switch x := x.(type) { case Float: @@ -1199,11 +1243,10 @@ func CompareDepth(op syntax.Token, x, y Value, depth int) (bool, error) { switch x := x.(type) { case Int: if y, ok := y.(Float); ok { - if y != y { - return false, nil // y is NaN - } var cmp int - if !math.IsInf(float64(y), 0) { + if y != y { + cmp = -1 // y is NaN + } else if !math.IsInf(float64(y), 0) { cmp = x.rational().Cmp(y.rational()) // y is finite } else if y > 0 { cmp = -1 // y is +Inf @@ -1214,16 +1257,15 @@ func CompareDepth(op syntax.Token, x, y Value, depth int) (bool, error) { } case Float: if y, ok := y.(Int); ok { - if x != x { - return false, nil // x is NaN - } var cmp int - if !math.IsInf(float64(x), 0) { + if x != x { + cmp = +1 // x is NaN + } else if !math.IsInf(float64(x), 0) { cmp = x.rational().Cmp(y.rational()) // x is finite } else if x > 0 { - cmp = -1 // x is +Inf + cmp = +1 // x is +Inf } else { - cmp = +1 // x is -Inf + cmp = -1 // x is -Inf } return threeway(op, cmp), nil } |