Editing Dc (computer program) (section)

===Integer factorization===

<syntaxhighlight lang="bash">
dc -e '[n=]P?[p]s2[lip/dli%0=1dvsr]s12sid2%0=13sidvsr[dli%0=1lrli2+dsi!>.]ds.xd1<2'
</syntaxhighlight>
This program was also written by Michel Charpentier.<ref>{{cite web
|url=https://tldp.org/LDP/abs/html/mathc.html
|title=Advanced Bash-Scripting Guide, Chapter 16, Example 16-52 (Factorization)
|access-date=2020-09-20
}}</ref> 

There is a shorter
<syntaxhighlight lang="bash">
dc -e "[n=]P?[lfp/dlf%0=Fdvsr]sF[dsf]sJdvsr2sf[dlf%0=Flfdd2%+1+sflr<Jd1<M]dsMx"
</syntaxhighlight>

and a faster solution (try with the 200-bit number {{math|2<sup>200</sup>-1}} (input <code>2 200^1-</code>)
<syntaxhighlight lang="bash">
dc -e "[n=]P?[lfp/dlf% 0=Fdvsr]sFdvsr2sfd2%0=F3sfd3%0=F5sf[dlf%0=Flfd4+sflr>M]sN[dlf%0=Flfd2+sflr>N]dsMx[p]sMd1<M" 
</syntaxhighlight>

Note that the latter can be sped up even more, if the access to a constant is replaced by a register access.

<syntaxhighlight lang="bash">
dc -e "[n=]P?[lfp/dlf%l0=Fdvsr]sF2s2dvsr2sf4s4d2%0=F3sfd3%0=F5sf[dlf%l0=Flfdl4+sflr>M]sN[dlf%l0=Flfdl2+sflr>N]dsMx[p]sMd1<M"
</syntaxhighlight>