Documentation says u128 is maximum integer but in a codebase we have mentions of u256

[achempion]

We have mentions of u256 but master documentation mentions only u128.

Also, we have bigint struct without any hints what it actually is and what maximum value it can represent, 300^40?

p.s. I don't have much experience in system programming

[tauoverpi]

There's a snippet below the table which covers the u256 case.

In addition to the integer types above, arbitrary bit-width integers can be referenced by using an identifier of i or u followed by digits. For example, the identifier i7 refers to a signed 7-bit integer. The maximum allowed bit-width of an integer type is 65535.

[achempion]

Didn't see that, thank you for pointing out, just searched the page for "u256".

But what is bigint for? Isn't u65535 can cover most of the needs for big numbers?

[ifreund]

But what is bigint for? Isn't u65535 can cover most of the needs for big numbers?

u65535 is big, but it's not arbitrarily big/small to fit your needs. The bigint implementation in the std is used to implement comptime_ints in the self hosted compiler.