This function is used as operator for the type mapping(int16 => uint256)
.
Basically in solidity you can attach functions to a type using a Using A for B
syntax. The first argument of these function is special, and it's easier to understand looking at some examples.
So, in your case the code will have a library with some functions that all perform some operation on mapping(int16 => uint256)
. This is type B
, and will appear as the first argument in the functions:
library LibraryName {
function nextInitializedTickWithinOneWord(
mapping(int16 => uint256) storage self,
int24 tick,
int24 tickSpacing,
bool lte
) internal view returns (int24 next, bool initialized) {
...
}
}
The main contract has a variable ticks
of this type. Importing the library and using the syntax Using A for B
, we can perform all the functions like this:
using LibraryName for mapping(int16 => uint256);
mapping(int16 => uint256) public ticks;
ticks.nextInitializedTickWithinOneWord(
_tick,
_tickSpacing,
_lte
);
which is equivalent of doing:
LibraryName.nextInitializedTickWithinOneWord(
ticks,
_tick,
_tickSpacing,
_lte
);
Check the docs here for a other examples. A common one is Using SafeERC20 for IERC20
, you have a function function safeTransfer(IERC20 token, address to, uint256 amount)
that you call with token.safeTransfer(to, amount)
. So the first argument of the function is written "outside" kinda.
Hope it's clear. I can't help with the second question, maybe you're asking the meaning of <<
and &
? If so, 1 << bitPos
is basically 2**bitPos
, and &
is bitwise AND. In any case I agree it's better to ask it in a separate question.