Typemax for T <: Integer if T can be BigInt?

General Usage
1

I am trying to keep a function generic with regard to its integer arguments. One of the function portions is

if  n > typemax(T) ÷ k
    break
end

and since T is Integer and could be BigInt, I would like a suggestion what to do about

julia> typemax(BigInt)
ERROR: MethodError: no method matching typemax(::Type{BigInt})
2

There are at least two approaches. One will be more appropriate. To write the function so BigInts are not accepted but all other built-in Integer types (or so all other built-in Signed Integer types) are accepted:

function for_builtin_fixedsize_integers(x::Base.BitInteger) ...
function for_builtin_fixedsuze_signedintegers(x::Base.BitSigned) ...

To accept BigInts and avoid the error that typemax(BigInt) triggers
(a) rewrite your function so typemax(T) is not used
or
(b) rewrite your function so typemax(BigInt) is avoided
consider using

const MaxBigInt = # whatever you choose
function avoids_error(x) # or (x::Signed) or (x::Integer)
   # code
   maxint = x isa BigInt ?  MaxBigInt : typemax(typeof(x))
   # code
end

or an approach similar to

function avoids_error(x) # or (x::Signed) or (x::Integer)
   # code
   maxint = x isa BigInt ?  x^2: typemax(typeof(x))
   # code
end
3

You can use the Base.hastypemax trait, in order to conditionally make a check only for bounded integer types, e.g.

if  hastypemax(T) && n > typemax(T) ÷ k
    break
end

Note that Base.hastypemax is currently not public API, there is an issue on this: Rational of `Base.hastypemax(BigInt)` (not exported) vs `typemax(BigInt) = Inf` · Issue #39344 · JuliaLang/julia · GitHub.

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