constant

Documentation

Overview

Package constant provides functionality for working with constant values and functions. It includes a set of predefined functions that can be called dynamically, as well as utility functions for type conversion and assertion.

Package constant implements Values representing untyped Next constants and their corresponding operations.

Index

• func BitLen(x Value) int
• func BoolVal(x Value) bool
• func Bytes(x Value) []byte
• func Compare(x_ Value, op token.Token, y_ Value) bool
• func Float32Val(x Value) (float32, bool)
• func Float64Val(x Value) (float64, bool)
• func Int64Val(x Value) (int64, bool)
• func Sign(x Value) int
• func StringVal(x Value) string
• func Uint64Val(x Value) (uint64, bool)
• func Underlying(value Value) any
• func Val(x Value) any
• type Func
• type FuncContext
• type Kind
  • func (i Kind) String() string
• type Value
  • func BinaryOp(x_ Value, op token.Token, y_ Value) Value
  • func Call(ctx FuncContext, fun string, args []Value) (v Value, err error)
  • func Denom(x Value) Value
  • func Make(x any) Value
  • func MakeBool(b bool) Value
  • func MakeFloat64(x float64) Value
  • func MakeFromBytes(bytes []byte) Value
  • func MakeFromLiteral(lit string, tok token.Token, zero uint) Value
  • func MakeInt64(x int64) Value
  • func MakeString(s string) Value
  • func MakeUint64(x uint64) Value
  • func MakeUnknown() Value
  • func Num(x Value) Value
  • func Or(x, y Value) Value
  • func Shift(x Value, op token.Token, s uint) Value
  • func ToFloat(x Value) Value
  • func ToInt(x Value) Value
  • func UnaryOp(op token.Token, y Value, prec uint) Value

Functions

func BitLen

func BitLen(x Value) int

BitLen returns the number of bits required to represent the absolute value x in binary representation; x must be an Int or an Unknown. If x is Unknown, the result is 0.

func BoolVal

func BoolVal(x Value) bool

BoolVal returns the Go boolean value of x, which must be a Bool or an Unknown. If x is Unknown, the result is false.

func Bytes

func Bytes(x Value) []byte

Bytes returns the bytes for the absolute value of x in little- endian binary representation; x must be an Int.

func Compare

func Compare(x_ Value, op token.Token, y_ Value) bool

Compare returns the result of the comparison x op y. The comparison must be defined for the operands. If one of the operands is Unknown, the result is false.

func Float32Val

func Float32Val(x Value) (float32, bool)

Float32Val returns the nearest Go float32 value of x and whether the result is exact; x must be numeric or Unknown. For values too small (too close to 0) to represent as float32, Float32Val silently underflows to 0. If x is Unknown, the result is (0, false).

func Float64Val

func Float64Val(x Value) (float64, bool)

Float64Val returns the nearest Go float64 value of x and whether the result is exact; x must be numeric or Unknown. For values too small (too close to 0) to represent as float64, Float64Val silently underflows to 0. The result sign always matches the sign of x, even for 0. If x is Unknown, the result is (0, false).

func Int64Val

func Int64Val(x Value) (int64, bool)

Int64Val returns the Go int64 value of x and whether the result is exact; x must be an Int or an Unknown. If the result is not exact, its value is undefined. If x is Unknown, the result is (0, false).

func Sign

func Sign(x Value) int

Sign returns -1, 0, or 1 depending on whether x < 0, x == 0, or x > 0; x must be numeric or Unknown. If x is Unknown, the result is 1.

func StringVal

func StringVal(x Value) string

StringVal returns the Go string value of x, which must be a String or an Unknown. If x is Unknown, the result is "".

func Uint64Val

func Uint64Val(x Value) (uint64, bool)

Uint64Val returns the Go uint64 value of x and whether the result is exact; x must be an Int or an Unknown. If the result is not exact, its value is undefined. If x is Unknown, the result is (0, false).

func Underlying

func Underlying(value Value) any

Underlying returns the underlying value of a Value, if it is a simple type.:w

func Val

func Val(x Value) any

Val returns the underlying value for a given constant. Since it returns an interface, it is up to the caller to type assert the result to the expected type.

Types

type Func

type Func func(ctx FuncContext, args []Value) Value

Func represents a function that can be called with a FuncContext and arguments.

type FuncContext

type FuncContext interface {
	Debug(msg string, args ...any)
	Error(args ...any)
	Getenv(name string) (string, bool)
}

FuncContext represents the context in which a function is executed. It provides methods for debugging, printing, and error reporting.

type Kind

type Kind int

Kind specifies the kind of value represented by a Value.

const (
	Unknown Kind = iota // unknown values
	Bool                // boolean values
	String              // string values
	Int                 // integer values
	Float               // floating-point values
)

func (Kind) String

func (i Kind) String() string

type Value

type Value interface {
	// Kind returns the value kind.
	Kind() Kind

	// String returns a short, quoted (human-readable) form of the value.
	// For numeric values, the result may be an approximation;
	// for String values the result may be a shortened string.
	// Use ExactString for a string representing a value exactly.
	String() string

	// ExactString returns an exact, quoted (human-readable) form of the value.
	// If the Value is of Kind String, use StringVal to obtain the unquoted string.
	ExactString() string
	// contains filtered or unexported methods
}

Value represents the value of a Go constant.

func BinaryOp

func BinaryOp(x_ Value, op token.Token, y_ Value) Value

BinaryOp returns the result of the binary expression x op y. The operation must be defined for the operands. If one of the operands is Unknown, the result is Unknown. BinaryOp doesn't handle comparisons or shifts; use Compare or Shift instead.

To force integer division of Int operands, use op == token.QUO_ASSIGN instead of token.QUO; the result is guaranteed to be Int in this case. Division by zero leads to a run-time panic.

func Call

func Call(ctx FuncContext, fun string, args []Value) (v Value, err error)

Call invokes the function named by fun with the provided arguments. It returns the result of the function call and any error that occurred.

func Denom

func Denom(x Value) Value

Denom returns the denominator of x; x must be Int, Float, or Unknown. If x is Unknown, or if it is too large or small to represent as a fraction, the result is Unknown. Otherwise the result is an Int >= 1.

func Make

func Make(x any) Value

Make returns the Value for x.

func MakeBool

func MakeBool(b bool) Value

MakeBool returns the Bool value for b.

func MakeFloat64

func MakeFloat64(x float64) Value

MakeFloat64 returns the Float value for x. If x is -0.0, the result is 0.0. If x is not finite, the result is Unknown.

func MakeFromBytes

func MakeFromBytes(bytes []byte) Value

MakeFromBytes returns the Int value given the bytes of its little-endian binary representation. An empty byte slice argument represents 0.

func MakeFromLiteral

func MakeFromLiteral(lit string, tok token.Token, zero uint) Value

MakeFromLiteral returns the corresponding integer, floating-point, imaginary, character, or string value for a Go literal string. The tok value must be one of token.INT, token.FLOAT, token.IMAG, token.CHAR, or token.STRING. The final argument must be zero. If the literal string syntax is invalid, the result is Unknown.

func MakeInt64

func MakeInt64(x int64) Value

MakeInt64 returns the Int value for x.

func MakeString

func MakeString(s string) Value

MakeString returns the String value for s.

func MakeUint64

func MakeUint64(x uint64) Value

MakeUint64 returns the Int value for x.

func MakeUnknown

func MakeUnknown() Value

MakeUnknown returns the Unknown value.

func Num

func Num(x Value) Value

Num returns the numerator of x; x must be Int, Float, or Unknown. If x is Unknown, or if it is too large or small to represent as a fraction, the result is Unknown. Otherwise the result is an Int with the same sign as x.

func Or

func Or(x, y Value) Value

Or returns the result of the value of x or y like in JavaScript.

- If y is unknown, the result is x. - If x is false, the result is y. - If x is 0, the result is y. - If x is "", the result is y. - Otherwise, the result is x.

func Shift

func Shift(x Value, op token.Token, s uint) Value

Shift returns the result of the shift expression x op s with op == token.SHL or token.SHR (<< or >>). x must be an Int or an Unknown. If x is Unknown, the result is x.

func ToFloat

func ToFloat(x Value) Value

ToFloat converts x to a Float value if x is representable as a Float. Otherwise it returns Unknown.

func ToInt

func ToInt(x Value) Value

ToInt converts x to an Int value if x is representable as an Int. Otherwise it returns Unknown.

func UnaryOp

func UnaryOp(op token.Token, y Value, prec uint) Value

UnaryOp returns the result of the unary expression op y. The operation must be defined for the operand. If prec > 0 it specifies the ^ (xor) result size in bits. If y is Unknown, the result is Unknown.