Fixed-width integers similar to builtin ones
43 Stars
Updated Last
7 Months Ago
Started In
September 2018


Tests Status

This package implements fixed-width integer types similar to standard builtin-ones like Int or UInt128. The following types, with obvious meaning, are exported: Int256, UInt256, Int512, UInt512, Int1024, UInt1024; they come with string macros to construct them (like for Int128 and UInt128), e.g. int256"123". It's possible to instantiate a new pair of types with the exported @define_integers macro:

julia> BitIntegers.@define_integers 24

julia> UInt24(1), Int24(2)
(0x000001, 2)

julia> BitIntegers.@define_integers 8 MyInt8 MyUInt8

julia> MyUInt8(1)

julia> myint8"123" # the string macro is named like the type, in lower case

This is implemented using primitive type and julia intrinsics, the caveat being that it might not always be legal (e.g. in some julia versions, Primes.factor(rand(UInt256)) used to make LLVM abort the program, while it was fine for Int256).

There are another couple of outstanding issues:

  1. the intrinsics for division operations used to make LLVM fail for widths greater than 128 bits, so they are here implemented via conversion to BigInt first, which makes them quite slow; it got slightly better in recent julia (nightly pre-1.10), where it prints JIT session error: Symbols not found: [ __divei4 ] but at least doesn't abort.

  2. prior to Julia version 1.2: for some reason, importing this code invalidates many precompiled functions from Base, so the REPL experience becomes very annoyingly slow until functions get recompiled (fixed by JuliaLang/julia#30830);

  3. prior to Julia version 1.4: creating arrays of types of size not a power of two easily leads to errors and segfaults (cf. e.g. #1, fixed by JuliaLang/julia#33283).

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