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Module Int_builtinsSource

In the following, the _untagged variant takes an untagged (i.e., C) int, whereas the normal variant takes an OCaml int. Which one to choose depends on the context: if you were previously doing integer operations, the compiler probably already compiled the untagged int, so using the _untagged version might be slightly faster (though probably barely noticeable). If you are reading from an argument or a field in a datastructure, your integer is tagged, so you should use the normal version.

Warning: for some corner arguments, the normal and untagged version may have different behaviours. In that case, we suffix the unsafe variant with _unsafe.

If in doubt, just use the normal version.

For non-zero numbers, log2 x is the position of the highest bit set, i.e. such that x lsr (log x) = 1. Numbers are interpreted as unsigned (e.g. (log2 -1) = 62 on 64-bit plateforms, as ints are 63-bit in OCaml.

Sourceval log2 : int -> int

In this version, log2 0 = -1.

Sourceval log2_untagged_unsafe : int -> int

Warning: log2_untagged_unsafe 0 = 1, which is probably not what you want. Furthermore, log2_untagged_unsafe x = 1 + log2 x when x is negative. log2_untagged_unsafe is thus safe only on strictly positive integer values.

Sourceval highest_bit : int -> int

highest_bit x is the value y where the only bit set is the most significant bit of x, i.e.

  • x land y = y
  • x land (lnot y) land (lnot y - 1) = 0. Furthermore, highest_bit 0 = 0.
Sourceval highest_bit_untagged_unsafe : int -> int

Like highest_bit, but highest_bit_untagged_unsafe 0 and highest_bit_untagged_unsafe x when x < 0 are undefined.

Sourceval ffs_untaggued : int -> int

See ffs.

Sourceval ffs : int -> int
Sourceval count_trailing_zeroes_untagged : int -> int
Sourceval count_trailing_zeroes : int -> int
Sourceval popcount : int -> int

popcount returns the number of bit set in the machine representation of the integer.

Sourceval popcount_untaggued : int -> int

See popcount.

Sourceval is_zero_or_a_power_of_2 : int -> bool
Sourceval is_a_power_of_2 : int -> bool