Member "ln" not found or not visible after argument-dependent lookup in type(SD59x18). about prb-math

[PaulRBerg]

SD59x18 something = SD59x18.ln(SD59x18.wrap(int256(2)));

It is not possible to use the functions defined in user-defined value types in this way.

The correct way is to access the functions by using the dot operator, like this:

SD59x18 x = SD59x18.wrap(2);
SD59x18 something = x.ln();

Alternatively, you could also import the ln function, like this:

import { ln } from "@prb/math/sd59x18/Math.sol";

SD59x18 x = SD59x18.wrap(2);
SD59x18 something = ln(x);

Finally, note that you can make the typecasting look prettier (more succinct) using the sd casting utility:

import { sd } from "@prb/math/SD59x18.sol";

SD59x18 x = sd(2);
SD59x18 something = x.ln();

Other functions such as wrap and div are working just fine.

wrap works because that's a built-in function compiler. div doesn't work, so I'm not sure how you got it working. This code does not compile:

SD59x18 x = SD59x18.wrap(2);
result = SD59x18.div(x, x);

the linter complains about assembly ("memory-safe")

That is not an issue with the linter but with the VSCode Solidity extension:

juanfranblanco/vscode-solidity#386