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Cast a constant for shifts > 14 steps #911

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Cast a constant for shifts > 14 steps #911

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9 changes: 9 additions & 0 deletions Language/Structure/Bitwise Operators/bitshiftLeft.adoc
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Expand Up @@ -62,6 +62,15 @@ int y = 14;
int result = x << y; // binary: 0100000000000000 - the first 1 in 101 was discarded
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Attention: Left-shifting a constant (like e.g. "1") means left-shifting a two-byte integer! If you want to shift it more than 14 steps to the left (e. g. for the use with a set of 4 daisy-chained shift registers), you will have to cast it, otherwise you won't get reasonable resluts:
[source,arduino]
----
uint32_t x1 = 1 << 14; // binary: 100000000000000
uint32_t x2 = 1 << 15; // binary: 11111111111111111000000000000000
uint32_t y1 = uint32_t(1) << 14; // binary: 100000000000000
uint32_t y2 = uint32_t(1) << 15; // binary: 1000000000000000
----

If you are certain that none of the ones in a value are being shifted into oblivion, a simple way to think of the left-shift operator is that it multiplies the left operand by 2 raised to the right operand power. For example, to generate powers of 2, the following expressions can be employed:

[source,arduino]
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