What is the correct max input for exp()?

[antoniopgs]

It looks like the max input for exp() is 133.084258667509499441:

• https://github.com/paulrberg/prb-math/blob/main/contracts/PRBMathUD60x18Typed.sol#L138
• https://github.com/paulrberg/prb-math/blob/main/contracts/PRBMath.sol#L73

However, here it says it's actually 88.722839111672999628:

• https://github.com/paulrberg/prb-math/blob/main/contracts/PRBMathUD60x18Typed.sol#L130

I'm assuming the former is correct and the latter is wrong. Right?

[PaulRBerg]

Good catch! You're right in that the former is correct, i.e. 133.084258667509499441.

This is a vestige of the original implementation of the exp function, which was using 128.128-bit as the internal number representation. Now I'm using 192.64-bit, which allows for better accuracy, hence a greater allowed input. You can read more about the history of this refactor in issue #32 and in commit 6d28ff. Such a shame that I didn't create a PR for this.

So this is just a documentation typo. I pushed a commit to fix it:

830eb44

[PaulRBerg]

For future reference: PRBMath now explicitly defines the maximum inputs allowed in exp and exp2:

• EXP_MAX_INPUT
• EXP2_MAX_INPUT