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'\" t
.\" Copyright (c) 2025 Bruce Hill
.\" All rights reserved.
.\"
.TH Int.prev_prime 3 2025-09-21 "Tomo man-pages"
.SH NAME
Int.prev_prime \- get the previous prime
.SH LIBRARY
Tomo Standard Library
.SH SYNOPSIS
.nf
.BI Int.prev_prime\ :\ func(x:\ Int\ ->\ Int?)
.fi
.SH DESCRIPTION
Finds the previous prime number less than the given integer. If there is no previous prime number (i.e. if a number less than `2` is provided), then the function will create a runtime error.
.SH ARGUMENTS
.TS
allbox;
lb lb lbx lb
l l l l.
Name Type Description Default
x Int The integer before which to find the previous prime. -
.TE
.SH RETURN
The previous prime number less than `x`, or `none` if `x` is less than 2.
.SH NOTES
This function is _probabilistic_, but the chances of getting an incorrect answer are astronomically small (on the order of 10^(-30)). See [the GNU MP docs](https://gmplib.org/manual/Number-Theoretic-Functions#index-mpz_005fprobab_005fprime_005fp) for more details.
.SH EXAMPLES
.EX
assert (11).prev_prime() == 7
.EE
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