Documentation ¶
Overview ¶
Package apd implements arbitrary-precision decimals.
apd implements much of the decimal specification from the General Decimal Arithmetic (http://speleotrove.com/decimal/) description, which is refered to here as GDA. This is the same specification implemented by pythons decimal module (https://docs.python.org/2/library/decimal.html) and GCCs decimal extension.
Features ¶
Panic-free operation. The math/big types don’t return errors, and instead panic under some conditions that are documented. This requires users to validate the inputs before using them. Meanwhile, we’d like our decimal operations to have more failure modes and more input requirements than the math/big types, so using that API would be difficult. apd instead returns errors when needed.
Support for standard functions. sqrt, ln, pow, etc.
Accurate and configurable precision. Operations will use enough internal precision to produce a correct result at the requested precision. Precision is set by a "context" structure that accompanies the function arguments, as discussed in the next section.
Good performance. Operations will either be fast enough or will produce an error if they will be slow. This prevents edge-case operations from consuming lots of CPU or memory.
Condition flags and traps. All operations will report whether their result is exact, is rounded, is over- or under-flowed, is subnormal (https://en.wikipedia.org/wiki/Denormal_number), or is some other condition. apd supports traps which will trigger an error on any of these conditions. This makes it possible to guarantee exactness in computations, if needed.
SQL scan and value methods are implemented. This allows the use of Decimals as placeholder parameters and row result Scan destinations.
Usage ¶
apd has two main types. The first is Decimal which holds the values of decimals. It is simple and uses a big.Int with an exponent to describe values. Most operations on Decimals can’t produce errors as they work directly on the underlying big.Int. Notably, however, there are no arithmetic operations on Decimals.
The second main type is Context, which is where all arithmetic operations are defined. A Context describes the precision, range, and some other restrictions during operations. These operations can all produce failures, and so return errors.
Context operations, in addition to errors, return a Condition, which is a bitfield of flags that occurred during an operation. These include overflow, underflow, inexact, rounded, and others. The Traps field of a Context can be set which will produce an error if the corresponding flag occurs. An example of this is given below.
Index ¶
- Constants
- Variables
- func NewFromString(s string) (*Decimal, Condition, error)
- func NumDigits(b *BigInt) int64
- type BigInt
- func (z *BigInt) Abs(x *BigInt) *BigInt
- func (z *BigInt) Add(x, y *BigInt) *BigInt
- func (z *BigInt) And(x, y *BigInt) *BigInt
- func (z *BigInt) AndNot(x, y *BigInt) *BigInt
- func (z *BigInt) Append(buf []byte, base int) []byte
- func (z *BigInt) Binomial(n, k int64) *BigInt
- func (z *BigInt) Bit(i int) uint
- func (z *BigInt) BitLen() int
- func (z *BigInt) Bits() []big.Word
- func (z *BigInt) Bytes() []byte
- func (z *BigInt) Cmp(y *BigInt) (r int)
- func (z *BigInt) CmpAbs(y *BigInt) (r int)
- func (z *BigInt) Div(x, y *BigInt) *BigInt
- func (z *BigInt) DivMod(x, y, m *BigInt) (*BigInt, *BigInt)
- func (z *BigInt) Exp(x, y, m *BigInt) *BigInt
- func (z *BigInt) FillBytes(buf []byte) []byte
- func (z *BigInt) Format(s fmt.State, ch rune)
- func (z *BigInt) GCD(x, y, a, b *BigInt) *BigInt
- func (z *BigInt) GobDecode(buf []byte) error
- func (z *BigInt) GobEncode() ([]byte, error)
- func (z *BigInt) Int64() int64
- func (z *BigInt) IsInt64() bool
- func (z *BigInt) IsUint64() bool
- func (z *BigInt) Lsh(x *BigInt, n uint) *BigInt
- func (z *BigInt) MarshalJSON() ([]byte, error)
- func (z *BigInt) MarshalText() (text []byte, err error)
- func (z *BigInt) MathBigInt() *big.Int
- func (z *BigInt) Mod(x, y *BigInt) *BigInt
- func (z *BigInt) ModInverse(g, n *BigInt) *BigInt
- func (z *BigInt) ModSqrt(x, p *BigInt) *BigInt
- func (z *BigInt) Mul(x, y *BigInt) *BigInt
- func (z *BigInt) MulRange(x, y int64) *BigInt
- func (z *BigInt) Neg(x *BigInt) *BigInt
- func (z *BigInt) Not(x *BigInt) *BigInt
- func (z *BigInt) Or(x, y *BigInt) *BigInt
- func (z *BigInt) ProbablyPrime(n int) bool
- func (z *BigInt) Quo(x, y *BigInt) *BigInt
- func (z *BigInt) QuoRem(x, y, r *BigInt) (*BigInt, *BigInt)
- func (z *BigInt) Rand(rnd *rand.Rand, n *BigInt) *BigInt
- func (z *BigInt) Rem(x, y *BigInt) *BigInt
- func (z *BigInt) Rsh(x *BigInt, n uint) *BigInt
- func (z *BigInt) Scan(s fmt.ScanState, ch rune) error
- func (z *BigInt) Set(x *BigInt) *BigInt
- func (z *BigInt) SetBit(x *BigInt, i int, b uint) *BigInt
- func (z *BigInt) SetBits(abs []big.Word) *BigInt
- func (z *BigInt) SetBytes(buf []byte) *BigInt
- func (z *BigInt) SetInt64(x int64) *BigInt
- func (z *BigInt) SetMathBigInt(x *big.Int) *BigInt
- func (z *BigInt) SetString(s string, base int) (*BigInt, bool)
- func (z *BigInt) SetUint64(x uint64) *BigInt
- func (z *BigInt) Sign() int
- func (z *BigInt) Size() uintptr
- func (z *BigInt) Sqrt(x *BigInt) *BigInt
- func (z *BigInt) String() string
- func (z *BigInt) Sub(x, y *BigInt) *BigInt
- func (z *BigInt) Text(base int) string
- func (z *BigInt) TrailingZeroBits() uint
- func (z *BigInt) Uint64() uint64
- func (z *BigInt) UnmarshalJSON(text []byte) error
- func (z *BigInt) UnmarshalText(text []byte) error
- func (z *BigInt) Xor(x, y *BigInt) *BigInt
- type Condition
- func (r Condition) Any() bool
- func (r Condition) Clamped() bool
- func (r Condition) DivisionByZero() bool
- func (r Condition) DivisionImpossible() bool
- func (r Condition) DivisionUndefined() bool
- func (r Condition) GoError(traps Condition) (Condition, error)
- func (r Condition) Inexact() bool
- func (r Condition) InvalidOperation() bool
- func (r Condition) Overflow() bool
- func (r Condition) Rounded() bool
- func (r Condition) String() string
- func (r Condition) Subnormal() bool
- func (r Condition) SystemOverflow() bool
- func (r Condition) SystemUnderflow() bool
- func (r Condition) Underflow() bool
- type Context
- func (c *Context) Abs(d, x *Decimal) (Condition, error)
- func (c *Context) Add(d, x, y *Decimal) (Condition, error)
- func (c *Context) Cbrt(d, x *Decimal) (Condition, error)
- func (c *Context) Ceil(d, x *Decimal) (Condition, error)
- func (c *Context) Cmp(d, x, y *Decimal) (Condition, error)
- func (c *Context) Exp(d, x *Decimal) (Condition, error)
- func (c *Context) Floor(d, x *Decimal) (Condition, error)
- func (c *Context) Ln(d, x *Decimal) (Condition, error)
- func (c *Context) Log10(d, x *Decimal) (Condition, error)
- func (c *Context) Mul(d, x, y *Decimal) (Condition, error)
- func (c *Context) Neg(d, x *Decimal) (Condition, error)
- func (c *Context) NewFromString(s string) (*Decimal, Condition, error)
- func (c *Context) Pow(d, x, y *Decimal) (Condition, error)
- func (c *Context) Quantize(d, x *Decimal, exp int32) (Condition, error)
- func (c *Context) Quo(d, x, y *Decimal) (Condition, error)
- func (c *Context) QuoInteger(d, x, y *Decimal) (Condition, error)
- func (c *Context) Reduce(d, x *Decimal) (int, Condition, error)
- func (c *Context) Rem(d, x, y *Decimal) (Condition, error)
- func (c *Context) Round(d, x *Decimal) (Condition, error)
- func (c *Context) RoundToIntegralExact(d, x *Decimal) (Condition, error)
- func (c *Context) RoundToIntegralValue(d, x *Decimal) (Condition, error)
- func (c *Context) SetString(d *Decimal, s string) (*Decimal, Condition, error)
- func (c *Context) Sqrt(d, x *Decimal) (Condition, error)
- func (c *Context) Sub(d, x, y *Decimal) (Condition, error)
- func (c *Context) WithPrecision(p uint32) *Context
- type Decimal
- func (d *Decimal) Abs(x *Decimal) *Decimal
- func (d *Decimal) Append(buf []byte, fmtString byte) []byte
- func (d *Decimal) Cmp(x *Decimal) int
- func (d *Decimal) CmpTotal(x *Decimal) int
- func (d *Decimal) Compose(form byte, negative bool, coefficient []byte, exponent int32) error
- func (d *Decimal) Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32)
- func (d *Decimal) Float64() (float64, error)
- func (d *Decimal) Format(s fmt.State, format rune)
- func (d *Decimal) Int64() (int64, error)
- func (d *Decimal) IsZero() bool
- func (d *Decimal) MarshalText() ([]byte, error)
- func (d *Decimal) Modf(integ, frac *Decimal)
- func (d *Decimal) Neg(x *Decimal) *Decimal
- func (d *Decimal) NumDigits() int64
- func (d *Decimal) Reduce(x *Decimal) (*Decimal, int)
- func (d *Decimal) Scan(src interface{}) error
- func (d *Decimal) Set(x *Decimal) *Decimal
- func (d *Decimal) SetFinite(x int64, e int32) *Decimal
- func (d *Decimal) SetFloat64(f float64) (*Decimal, error)
- func (d *Decimal) SetInt64(x int64) *Decimal
- func (d *Decimal) SetString(s string) (*Decimal, Condition, error)
- func (d *Decimal) Sign() int
- func (d *Decimal) Size() uintptr
- func (d *Decimal) String() string
- func (d *Decimal) Text(format byte) string
- func (d *Decimal) UnmarshalText(b []byte) error
- func (d Decimal) Value() (driver.Value, error)
- type ErrDecimal
- func (e *ErrDecimal) Abs(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Add(d, x, y *Decimal) *Decimal
- func (e *ErrDecimal) Ceil(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Err() error
- func (e *ErrDecimal) Exp(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Floor(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Int64(d *Decimal) int64
- func (e *ErrDecimal) Ln(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Log10(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Mul(d, x, y *Decimal) *Decimal
- func (e *ErrDecimal) Neg(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Pow(d, x, y *Decimal) *Decimal
- func (e *ErrDecimal) Quantize(d, v *Decimal, exp int32) *Decimal
- func (e *ErrDecimal) Quo(d, x, y *Decimal) *Decimal
- func (e *ErrDecimal) QuoInteger(d, x, y *Decimal) *Decimal
- func (e *ErrDecimal) Reduce(d, x *Decimal) (int, *Decimal)
- func (e *ErrDecimal) Rem(d, x, y *Decimal) *Decimal
- func (e *ErrDecimal) Round(d, x *Decimal) *Decimal
- func (e *ErrDecimal) RoundToIntegralExact(d, x *Decimal) *Decimal
- func (e *ErrDecimal) RoundToIntegralValue(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Sqrt(d, x *Decimal) *Decimal
- func (e *ErrDecimal) Sub(d, x, y *Decimal) *Decimal
- type Form
- type NullDecimal
- type Rounder
Examples ¶
Constants ¶
const ( // MaxExponent is the highest exponent supported. Exponents near this range will // perform very slowly (many seconds per operation). MaxExponent = 100000 // MinExponent is the lowest exponent supported with the same limitations as // MaxExponent. MinExponent = -MaxExponent )
const ( // DefaultTraps is the default trap set used by BaseContext. DefaultTraps = SystemOverflow | SystemUnderflow | Overflow | Underflow | Subnormal | DivisionUndefined | DivisionByZero | DivisionImpossible | InvalidOperation )
Variables ¶
var BaseContext = Context{ Precision: 0, MaxExponent: MaxExponent, MinExponent: MinExponent, Traps: DefaultTraps, }
BaseContext is a useful default Context. Should not be mutated.
Functions ¶
func NewFromString ¶
NewFromString creates a new decimal from s. It has no restrictions on exponents or precision.
Types ¶
type BigInt ¶
type BigInt struct {
// contains filtered or unexported fields
}
BigInt is a wrapper around big.Int. It minimizes memory allocation by using an inline array to back the big.Int's variable-length "nat" slice when the integer's value is sufficiently small. The zero value is ready to use.
func NewBigInt ¶
NewBigInt allocates and returns a new BigInt set to x.
NOTE: BigInt jumps through hoops to avoid escaping to the heap. As such, most users of BigInt should not need this function. They should instead declare a zero-valued BigInt directly on the stack and interact with references to this stack-allocated value. Recall that the zero-valued BigInt is ready to use.
func (*BigInt) MarshalJSON ¶
MarshalJSON calls (big.Int).MarshalJSON.
func (*BigInt) MarshalText ¶
MarshalText calls (big.Int).MarshalText.
func (*BigInt) MathBigInt ¶
MathBigInt returns the math/big.Int representation of z.
func (*BigInt) ModInverse ¶
ModInverse calls (big.Int).ModInverse.
func (*BigInt) ProbablyPrime ¶
ProbablyPrime calls (big.Int).ProbablyPrime.
func (*BigInt) SetMathBigInt ¶
SetMathBigInt sets z to x and returns z.
func (*BigInt) TrailingZeroBits ¶
TrailingZeroBits calls (big.Int).TrailingZeroBits.
func (*BigInt) UnmarshalJSON ¶
UnmarshalJSON calls (big.Int).UnmarshalJSON.
func (*BigInt) UnmarshalText ¶
UnmarshalText calls (big.Int).UnmarshalText.
type Condition ¶
type Condition uint32
Condition holds condition flags.
const ( // SystemOverflow is raised when an exponent is greater than MaxExponent. SystemOverflow Condition = 1 << iota // SystemUnderflow is raised when an exponent is less than MinExponent. SystemUnderflow // Overflow is raised when the exponent of a result is too large to be // represented. Overflow // Underflow is raised when a result is both subnormal and inexact. Underflow // Inexact is raised when a result is not exact (one or more non-zero // coefficient digits were discarded during rounding). Inexact // Subnormal is raised when a result is subnormal (its adjusted exponent is // less than Emin), before any rounding. Subnormal // Rounded is raised when a result has been rounded (that is, some zero or // non-zero coefficient digits were discarded). Rounded // DivisionUndefined is raised when both division operands are 0. DivisionUndefined // DivisionByZero is raised when a non-zero dividend is divided by zero. DivisionByZero // DivisionImpossible is raised when integer division cannot be exactly // represented with the given precision. DivisionImpossible // InvalidOperation is raised when a result would be undefined or impossible. InvalidOperation // Clamped is raised when the exponent of a result has been altered or // constrained in order to fit the constraints of the Decimal representation. Clamped )
func (Condition) DivisionByZero ¶
DivisionByZero returns true if the DivisionByZero flag is set.
func (Condition) DivisionImpossible ¶
DivisionImpossible returns true if the DivisionImpossible flag is set.
func (Condition) DivisionUndefined ¶
DivisionUndefined returns true if the DivisionUndefined flag is set.
func (Condition) GoError ¶
GoError converts r to an error based on the given traps and returns r. Traps are the conditions which will trigger an error result if the corresponding Flag condition occurred.
func (Condition) InvalidOperation ¶
InvalidOperation returns true if the InvalidOperation flag is set.
func (Condition) SystemOverflow ¶
SystemOverflow returns true if the SystemOverflow flag is set.
func (Condition) SystemUnderflow ¶
SystemUnderflow returns true if the SystemUnderflow flag is set.
type Context ¶
type Context struct { // Precision is the number of places to round during rounding; this is // effectively the total number of digits (before and after the decimal // point). Precision uint32 // MaxExponent specifies the largest effective exponent. The // effective exponent is the value of the Decimal in scientific notation. That // is, for 10e2, the effective exponent is 3 (1.0e3). Zero (0) is not a special // value; it does not disable this check. MaxExponent int32 // MinExponent is similar to MaxExponent, but for the smallest effective // exponent. MinExponent int32 // Traps are the conditions which will trigger an error result if the // corresponding Flag condition occurred. Traps Condition // Rounding specifies the Rounder to use during rounding. RoundHalfUp is used if // empty or not present in Roundings. Rounding Rounder }
Context maintains options for Decimal operations. It can safely be used concurrently, but not modified concurrently. Arguments for any method can safely be used as both result and operand.
Example (Inexact) ¶
ExampleInexact demonstrates how to detect inexact operations.
d := apd.New(27, 0) three := apd.New(3, 0) c := apd.BaseContext.WithPrecision(5) for { res, err := c.Quo(d, d, three) fmt.Printf("d: %7s, inexact: %5v, err: %v\n", d, res.Inexact(), err) if err != nil { return } if res.Inexact() { return } }
Output: d: 9.0000, inexact: false, err: <nil> d: 3.0000, inexact: false, err: <nil> d: 1.0000, inexact: false, err: <nil> d: 0.33333, inexact: true, err: <nil>
Example (Overflow) ¶
ExampleOverflow demonstrates how to detect or error on overflow.
// Create a context that will overflow at 1e3. c := apd.Context{ MaxExponent: 2, Traps: apd.Overflow, } one := apd.New(1, 0) d := apd.New(997, 0) for { res, err := c.Add(d, d, one) fmt.Printf("d: %8s, overflow: %5v, err: %v\n", d, res.Overflow(), err) if err != nil { return } }
Output: d: 998, overflow: false, err: <nil> d: 999, overflow: false, err: <nil> d: Infinity, overflow: true, err: overflow
func (*Context) Cmp ¶
Cmp compares x and y and sets d to:
-1 if x < y 0 if x == y +1 if x > y
This comparison respects the normal rules of special values (like NaN), and does not compare them.
func (*Context) NewFromString ¶
NewFromString creates a new decimal from s. The returned Decimal has its exponents restricted by the context and its value rounded if it contains more digits than the context's precision.
func (*Context) Quantize ¶
Quantize adjusts and rounds x as necessary so it is represented with exponent exp and stores the result in d.
Example ¶
input, _, _ := apd.NewFromString("123.45") output := new(apd.Decimal) c := apd.BaseContext.WithPrecision(10) for i := int32(-3); i <= 3; i++ { res, _ := c.Quantize(output, input, i) fmt.Printf("%2v: %s", i, output) if res != 0 { fmt.Printf(" (%s)", res) } fmt.Println() }
Output: -3: 123.450 -2: 123.45 -1: 123.5 (inexact, rounded) 0: 123 (inexact, rounded) 1: 1.2E+2 (inexact, rounded) 2: 1E+2 (inexact, rounded) 3: 0E+3 (inexact, rounded)
func (*Context) Quo ¶
Quo sets d to the quotient x/y for y != 0. c.Precision must be > 0. If an exact division is required, use a context with high precision and verify it was exact by checking the Inexact flag on the return Condition.
func (*Context) QuoInteger ¶
QuoInteger sets d to the integer part of the quotient x/y. If the result cannot fit in d.Precision digits, an error is returned.
func (*Context) Reduce ¶
Reduce sets d to x with all trailing zeros removed and returns the number of zeros removed.
func (*Context) Rem ¶
Rem sets d to the remainder part of the quotient x/y. If the integer part cannot fit in d.Precision digits, an error is returned.
func (*Context) Round ¶
Round sets d to rounded x, rounded to the precision specified by c. If c has zero precision, no rounding will occur. If c has no Rounding specified, RoundHalfUp is used.
func (*Context) RoundToIntegralExact ¶
RoundToIntegralExact sets d to integral value of x.
Example ¶
ExampleRoundToIntegralExact demonstrates how to use RoundToIntegralExact to check if a number is an integer or not. Note the variations between integer (which allows zeros after the decimal point) and strict (which does not). See the documentation on Inexact and Rounded.
inputs := []string{ "123.4", "123.0", "123", "12E1", "120E-1", "120E-2", } for _, input := range inputs { d, _, _ := apd.NewFromString(input) res, _ := apd.BaseContext.RoundToIntegralExact(d, d) integer := !res.Inexact() strict := !res.Rounded() fmt.Printf("input: % 6s, output: %3s, integer: %5t, strict: %5t, res:", input, d, integer, strict) if res != 0 { fmt.Printf(" %s", res) } fmt.Println() }
Output: input: 123.4, output: 123, integer: false, strict: false, res: inexact, rounded input: 123.0, output: 123, integer: true, strict: false, res: rounded input: 123, output: 123, integer: true, strict: true, res: input: 12E1, output: 120, integer: true, strict: true, res: input: 120E-1, output: 12, integer: true, strict: false, res: rounded input: 120E-2, output: 1, integer: false, strict: false, res: inexact, rounded
func (*Context) RoundToIntegralValue ¶
RoundToIntegralValue sets d to integral value of x. Inexact and Rounded flags are ignored and removed.
func (*Context) SetString ¶
SetString sets d to s and returns d. The returned Decimal has its exponents restricted by the context and its value rounded if it contains more digits than the context's precision.
func (*Context) Sqrt ¶
Sqrt sets d to the square root of x. Sqrt uses the Babylonian method for computing the square root, which uses O(log p) steps for p digits of precision.
func (*Context) WithPrecision ¶
WithPrecision returns a copy of c but with the specified precision.
type Decimal ¶
Decimal is an arbitrary-precision decimal. Its value is:
Negative × Coeff × 10**Exponent
Coeff must be positive. If it is negative results may be incorrect and apd may panic.
func NewWithBigInt ¶
NewWithBigInt creates a new decimal with the given coefficient and exponent.
func (*Decimal) Append ¶
Append appends to buf the string form of the decimal number d, as generated by d.Text, and returns the extended buffer.
func (*Decimal) Cmp ¶
Cmp compares d and x and returns:
-1 if d < x 0 if d == x +1 if d > x undefined if d or x are NaN
func (*Decimal) CmpTotal ¶
CmpTotal compares d and x using their abstract representation rather than their numerical value. A total ordering is defined for all possible abstract representations, as described below. If the first operand is lower in the total order than the second operand then the result is -1, if the operands have the same abstract representation then the result is 0, and if the first operand is higher in the total order than the second operand then the result is 1.
Numbers (representations which are not NaNs) are ordered such that a larger numerical value is higher in the ordering. If two representations have the same numerical value then the exponent is taken into account; larger (more positive) exponents are higher in the ordering.
For example, the following values are ordered from lowest to highest. Note the difference in ordering between 1.2300 and 1.23.
-NaN -NaNSignaling -Infinity -127 -1.00 -1 -0.000 -0 0 1.2300 1.23 1E+9 Infinity NaNSignaling NaN
func (*Decimal) Compose ¶
Compose sets the internal decimal value from parts. If the value cannot be represented then an error should be returned.
func (*Decimal) Decompose ¶
func (d *Decimal) Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32)
Decompose returns the internal decimal state into parts. If the provided buf has sufficient capacity, buf may be returned as the coefficient with the value set and length set as appropriate.
func (*Decimal) Float64 ¶
Float64 returns the float64 representation of x. This conversion may lose data (see strconv.ParseFloat for caveats).
func (*Decimal) Format ¶
Format implements fmt.Formatter. It accepts many of the regular formats for floating-point numbers ('e', 'E', 'f', 'F', 'g', 'G') as well as 's' and 'v', which are handled like 'G'. Format also supports the output field width, as well as the format flags '+' and ' ' for sign control, '0' for space or zero padding, and '-' for left or right justification. It does not support precision. See the fmt package for details.
func (*Decimal) Int64 ¶
Int64 returns the int64 representation of x. If x cannot be represented in an int64, an error is returned.
func (*Decimal) MarshalText ¶
MarshalText implements the encoding.TextMarshaler interface.
func (*Decimal) Modf ¶
Modf sets integ to the integral part of d and frac to the fractional part such that d = integ+frac. If d is negative, both integ or frac will be either 0 or negative. integ.Exponent will be >= 0; frac.Exponent will be <= 0. Either argument can be nil, preventing it from being set.
func (*Decimal) Reduce ¶
Reduce sets d to x with all trailing zeros removed and returns d and the number of zeros removed.
func (*Decimal) Scan ¶
Scan implements the database/sql.Scanner interface. It supports string, []byte, int64, float64.
func (*Decimal) SetFloat64 ¶
SetFloat64 sets d's Coefficient and Exponent to x and returns d. d will hold the exact value of f.
func (*Decimal) SetString ¶
SetString sets d to s and returns d. It has no restrictions on exponents or precision.
func (*Decimal) Sign ¶
Sign returns, if d is Finite:
-1 if d < 0 0 if d == 0 or -0 +1 if d > 0
Otherwise (if d is Infinite or NaN):
-1 if d.Negative == true +1 if d.Negative == false
func (*Decimal) String ¶
String formats x like x.Text('G'). It matches the to-scientific-string conversion of the GDA spec.
func (*Decimal) Text ¶
Text converts the floating-point number x to a string according to the given format. The format is one of:
'e' -d.dddde±dd, decimal exponent, exponent digits 'E' -d.ddddE±dd, decimal exponent, exponent digits 'f' -ddddd.dddd, no exponent 'g' like 'e' for large exponents, like 'f' otherwise 'G' like 'E' for large exponents, like 'f' otherwise
If format is a different character, Text returns a "%" followed by the unrecognized.Format character. The 'f' format has the possibility of displaying precision that is not present in the Decimal when it appends zeros (the 'g' format avoids the use of 'f' in this case). All other formats always show the exact precision of the Decimal.
func (*Decimal) UnmarshalText ¶
UnmarshalText implements the encoding.TextUnmarshaler interface.
type ErrDecimal ¶
type ErrDecimal struct { Ctx *Context // Flags are the accumulated flags from operations. Flags Condition // contains filtered or unexported fields }
ErrDecimal performs operations on decimals and collects errors during operations. If an error is already set, the operation is skipped. Designed to be used for many operations in a row, with a single error check at the end.
Example ¶
c := apd.BaseContext.WithPrecision(5) ed := apd.MakeErrDecimal(c) d := apd.New(10, 0) fmt.Printf("%s, err: %v\n", d, ed.Err()) ed.Add(d, d, apd.New(2, 1)) // add 20 fmt.Printf("%s, err: %v\n", d, ed.Err()) ed.Quo(d, d, apd.New(0, 0)) // divide by zero fmt.Printf("%s, err: %v\n", d, ed.Err()) ed.Sub(d, d, apd.New(1, 0)) // attempt to subtract 1 // The subtraction doesn't occur and doesn't change the error. fmt.Printf("%s, err: %v\n", d, ed.Err())
Output: 10, err: <nil> 30, err: <nil> Infinity, err: division by zero Infinity, err: division by zero
func MakeErrDecimal ¶
func MakeErrDecimal(c *Context) ErrDecimal
MakeErrDecimal creates a ErrDecimal with given context.
func (*ErrDecimal) Abs ¶
func (e *ErrDecimal) Abs(d, x *Decimal) *Decimal
Abs performs e.Ctx.Abs(d, x) and returns d.
func (*ErrDecimal) Add ¶
func (e *ErrDecimal) Add(d, x, y *Decimal) *Decimal
Add performs e.Ctx.Add(d, x, y) and returns d.
func (*ErrDecimal) Ceil ¶
func (e *ErrDecimal) Ceil(d, x *Decimal) *Decimal
Ceil performs e.Ctx.Ceil(d, x) and returns d.
func (*ErrDecimal) Err ¶
func (e *ErrDecimal) Err() error
Err returns the first error encountered or the context's trap error if present.
func (*ErrDecimal) Exp ¶
func (e *ErrDecimal) Exp(d, x *Decimal) *Decimal
Exp performs e.Ctx.Exp(d, x) and returns d.
func (*ErrDecimal) Floor ¶
func (e *ErrDecimal) Floor(d, x *Decimal) *Decimal
Floor performs e.Ctx.Floor(d, x) and returns d.
func (*ErrDecimal) Int64 ¶
func (e *ErrDecimal) Int64(d *Decimal) int64
Int64 returns 0 if err is set. Otherwise returns d.Int64().
func (*ErrDecimal) Ln ¶
func (e *ErrDecimal) Ln(d, x *Decimal) *Decimal
Ln performs e.Ctx.Ln(d, x) and returns d.
func (*ErrDecimal) Log10 ¶
func (e *ErrDecimal) Log10(d, x *Decimal) *Decimal
Log10 performs d.Log10(x) and returns d.
func (*ErrDecimal) Mul ¶
func (e *ErrDecimal) Mul(d, x, y *Decimal) *Decimal
Mul performs e.Ctx.Mul(d, x, y) and returns d.
func (*ErrDecimal) Neg ¶
func (e *ErrDecimal) Neg(d, x *Decimal) *Decimal
Neg performs e.Ctx.Neg(d, x) and returns d.
func (*ErrDecimal) Pow ¶
func (e *ErrDecimal) Pow(d, x, y *Decimal) *Decimal
Pow performs e.Ctx.Pow(d, x, y) and returns d.
func (*ErrDecimal) Quantize ¶
func (e *ErrDecimal) Quantize(d, v *Decimal, exp int32) *Decimal
Quantize performs e.Ctx.Quantize(d, v, exp) and returns d.
func (*ErrDecimal) Quo ¶
func (e *ErrDecimal) Quo(d, x, y *Decimal) *Decimal
Quo performs e.Ctx.Quo(d, x, y) and returns d.
func (*ErrDecimal) QuoInteger ¶
func (e *ErrDecimal) QuoInteger(d, x, y *Decimal) *Decimal
QuoInteger performs e.Ctx.QuoInteger(d, x, y) and returns d.
func (*ErrDecimal) Reduce ¶
func (e *ErrDecimal) Reduce(d, x *Decimal) (int, *Decimal)
Reduce performs e.Ctx.Reduce(d, x) and returns the number of zeros removed and d.
func (*ErrDecimal) Rem ¶
func (e *ErrDecimal) Rem(d, x, y *Decimal) *Decimal
Rem performs e.Ctx.Rem(d, x, y) and returns d.
func (*ErrDecimal) Round ¶
func (e *ErrDecimal) Round(d, x *Decimal) *Decimal
Round performs e.Ctx.Round(d, x) and returns d.
func (*ErrDecimal) RoundToIntegralExact ¶
func (e *ErrDecimal) RoundToIntegralExact(d, x *Decimal) *Decimal
RoundToIntegralExact performs e.Ctx.RoundToIntegralExact(d, x) and returns d.
func (*ErrDecimal) RoundToIntegralValue ¶
func (e *ErrDecimal) RoundToIntegralValue(d, x *Decimal) *Decimal
RoundToIntegralValue performs e.Ctx.RoundToIntegralValue(d, x) and returns d.
func (*ErrDecimal) Sqrt ¶
func (e *ErrDecimal) Sqrt(d, x *Decimal) *Decimal
Sqrt performs e.Ctx.Sqrt(d, x) and returns d.
func (*ErrDecimal) Sub ¶
func (e *ErrDecimal) Sub(d, x, y *Decimal) *Decimal
Sub performs e.Ctx.Sub(d, x, y) and returns d.
type NullDecimal ¶
NullDecimal represents a string that may be null. NullDecimal implements the database/sql.Scanner interface so it can be used as a scan destination:
var d NullDecimal err := db.QueryRow("SELECT num FROM foo WHERE id=?", id).Scan(&d) ... if d.Valid { // use d.Decimal } else { // NULL value }
func (*NullDecimal) Scan ¶
func (nd *NullDecimal) Scan(value interface{}) error
Scan implements the database/sql.Scanner interface.
type Rounder ¶
type Rounder string
Rounder specifies the behavior of rounding.
const ( // RoundDown rounds toward 0; truncate. RoundDown Rounder = "down" // RoundHalfUp rounds up if the digits are >= 0.5. RoundHalfUp Rounder = "half_up" // RoundHalfEven rounds up if the digits are > 0.5. If the digits are equal // to 0.5, it rounds up if the previous digit is odd, always producing an // even digit. RoundHalfEven Rounder = "half_even" // RoundCeiling towards +Inf: rounds up if digits are > 0 and the number // is positive. RoundCeiling Rounder = "ceiling" // RoundFloor towards -Inf: rounds up if digits are > 0 and the number // is negative. RoundFloor Rounder = "floor" // RoundHalfDown rounds up if the digits are > 0.5. RoundHalfDown Rounder = "half_down" // RoundUp rounds away from 0. RoundUp Rounder = "up" // Round05Up rounds zero or five away from 0; same as round-up, except that // rounding up only occurs if the digit to be rounded up is 0 or 5. Round05Up Rounder = "05up" )
func (Rounder) ShouldAddOne ¶
ShouldAddOne returns true if 1 should be added to the absolute value of a number being rounded. result is the result to which the 1 would be added. neg is true if the number is negative. half is -1 if the discarded digits are < 0.5, 0 if = 0.5, or 1 if > 0.5.