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What does these conditionals means? ($i < (1 << $len)) … ($i & (1 << $j))

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I am trying to understand a PHP code but it use a form of grouping conditionals that I do not know and I cannot find in the documentation:


for ($i = 1; $i < (1 << $len); $i++){...}


if ($i & (1 << $j)){...}


Any one know what is the normal form of these conditionals with && and ||?



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Those aren't conditionals, they're bitwise operators


<< will move bits of the left operand to the left by the amount specified on the right operand.


1 << $len is equivalent to 1 * pow(2, $len) (see pow() ) but much more efficient because computers operate in base 2 naturally.


The & operator operates in binary. It compares each 0 or 1 from a binary number with the 0 or 1 from another binary number and the result has a 1 if both of them were 1, 0 if not.

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