SHL: Difference between revisions

Revision as of 00:06, 22 April 2022

The _SHL function is used to shift the bits of a numerical value to the left.

result = _SHL(numericalVariable, numericalValue)

numericalVariable is the variable to shift the bits of and can be of the following types: INTEGER, LONG,_INTEGER64, or _BYTE.
Integer values can be signed or _UNSIGNED.
numericalValue is the number of places to shift the bits.
While 0 is a valid value it will have no affect on the variable being shifted.

Allows for multiplication of a value by 2 faster than normal multiplication (see example 2 below).
Bits that reach the end of a variable's bit count are dropped (when using a variable of the same type - otherwise they will carry over).
The type of variable used to store the results should match the type of the variable being shifted.

Example 1:

A~%% = 1 'set right most bit of an_UNSIGNED _BYTE
PRINT A~%%
PRINT _SHL(A~%%,7)
B~%% = _SHL(A~%%,8) 'shift the bit off the left 'edge'
PRINT B~%%

 1
 128
 0

Example 2:

A~%% = 1
FOR I%% = 0 TO 8
    PRINT _SHL(A~%%, I%%)
NEXT I%%

Note: When directly PRINTing to screen, the result is calculated internally using a larger variable type so the left most bit is carried to the next value.
- To avoid this store the result in a variable of the same type before printing.

@@ Line 44: / Line 44: @@
 {{Cl|FOR}} I%% = 0 {{Cl|TO}} 8
      {{Cl|PRINT}} {{Cl|_SHL}}(A~%%, I%%)
-{{Cl|NEXT I%%}}
+{{Cl|FOR...NEXT|NEXT}} I%%
 {{CodeEnd}}
 {{OutputStart}}