# package constant

`import "go/constant"`

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

A special Unknown value may be used when a value is unknown due to an error. Operations on unknown values produce unknown values unless specified otherwise.

value.go

## func BitLen

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

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

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

## func Compare

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

Float32Val is like Float64Val but for float32 instead of float64.

## func Float64Val

Float64Val returns the nearest Go float64 value of x and whether the result is exact; x must be numeric or an Unknown, but not Complex. 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

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

Sign returns -1, 0, or 1 depending on whether x < 0, x == 0, or x > 0; x must be numeric or Unknown. For complex values x, the sign is 0 if x == 0, otherwise it is != 0. If x is Unknown, the result is 1.

## func StringVal

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

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).

## type Kind

Kind specifies the kind of value represented by a Value.

## type Value

A Value represents the value of a Go constant.

### func BinaryOp

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 Denom

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 Imag

Imag returns the imaginary part of x, which must be a numeric or unknown value. If x is Unknown, the result is Unknown.

### func MakeBool

MakeBool returns the Bool value for b.

### func MakeFloat64

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

### func MakeFromBytes

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

### func MakeFromLiteral

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 an Unknown.

### func MakeImag

MakeImag returns the Complex value x*i; x must be Int, Float, or Unknown. If x is Unknown, the result is Unknown.

### func MakeInt64

MakeInt64 returns the Int value for x.

### func MakeString

MakeString returns the String value for s.

### func MakeUint64

MakeUint64 returns the Int value for x.

### func MakeUnknown

MakeUnknown returns the Unknown value.

### func Num

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 Real

Real returns the real part of x, which must be a numeric or unknown value. If x is Unknown, the result is Unknown.

### func Shift

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 ToComplex

ToComplex converts x to a Complex value if x is representable as a Complex. Otherwise it returns an Unknown.

### func ToFloat

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

### func ToInt

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

### func UnaryOp

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.