ShiftRotateLeft

(twinBASIC) Rotates the bits of an integral value left by a given number of positions. The bits shifted out at the high end come back in at the low end.

Syntax: ShiftRotateLeft( number, shiftamount )

number: required An expression of an integral type: Byte, Integer, Long, LongLong, LongPtr, Currency or Boolean. Any other type, a Variant included, is compile error TB5023, first argument must be a simple integral type.
shiftamount: required A numeric expression giving the number of bit positions to rotate. It is converted to a Long.

The result has the type of number. The rotation works on all the bits of that type: 8 for a Byte, 16 for an Integer or a Boolean, 32 for a Long, 64 for a LongLong or a Currency, and 32 or 64 for a LongPtr, as the build is 32-bit or 64-bit. A Currency is rotated as the 64-bit integer that stores it, which is its value multiplied by 10,000.

The rotation count is taken modulo the number of bits, so rotating a Long by 32 gives the value unchanged, and by 33 the same as by 1. A negative shiftamount rotates right: rotating a Long left by -1 is the same as rotating it left by 31. No value of shiftamount raises an error.

Unlike the << operator, which discards the bits shifted out and fills with zeros, ShiftRotateLeft loses no bits: &H12345678 << 4 is &H23456780, and ShiftRotateLeft(&H12345678, 4) is &H23456781.

With constant arguments, the call is evaluated when the code is compiled, so it can be used in a Const declaration, an Enum member’s value or a Case expression.

Warning

In twinBASIC BETA 997, ShiftRotateLeft ignores the names of named arguments and takes its arguments in the order they are written: ShiftRotateLeft(ShiftAmount:=4, Number:=&H12345678) rotates 4 left by &H12345678 bits, and gives the Integer &H400. Write the arguments by position, number first.

Note

ShiftRotateLeft is a twinBASIC extension. VBA and VB6 have no function of this name: a call to it is the compile error Sub or Function not defined.

Example

Dim Value As Long = &H12345678
Debug.Print Hex(ShiftRotateLeft(Value, 4))      ' 23456781
Debug.Print Hex(ShiftRotateLeft(Value, 36))     ' 23456781
Debug.Print Hex(Value << 4)                     ' 23456780

Dim Flags As Byte = &H81
Debug.Print Hex(ShiftRotateLeft(Flags, 1))      ' 3

ShiftRotateLeft

Example

See Also