Rotate left 2 bits (like assembler)

[Mango]

I believe the following will rotate QB signed 16-bit integers 2 to the left. Note: this would be simpler if qb had unsigned data types.

Code:

DEFINT A-Z
CLS
DO
INPUT "gimme a number"; a
PRINT a; " (dec) == "; HEX$(a); " (hex)"


SignBit = a < 0         ' true if 16th bit is on
'PRINT SignBit
nextBit = ((a AND &H4000) = &H4000)  ' true if 15th bit is on
'PRINT nextBit
newSignBit = ((a AND &H2000) = &H2000)  ' true if 14th bit is on
'PRINT newSignBit

a = a AND &H1FFF '&H1fff == 0001 1111 1111 1111...clear the bits that will fall off before shifting to prevent overflow errors

a = a * 4  ' shift left 2 bits
a = a + (-2 * SignBit) 'add bit to 2's place
a = a + (-1 * nextBit) 'add bit to 1's place

IF newSignBit THEN a = a OR &H8000  'add sign if needed

PRINT "your number rotated left 2 bits is"
PRINT a; " (dec) == "; HEX$(a); " (hex)"

LOOP

Not the most elegant solution, but...