in reply to incrementing mixed letters and numbers
As poj pointed out, it's rather convenient with base conversion modules. I did a review of some generic ones in a blog article. You can also see shmem's interesting module on his followup thread: Math::Base.
With ntheory and an initial string in $v I'd use something like $v = todigitstring(fromdigits($v,36)+1,36);, possibly adding an extra argument if we want zero padding. Of course we'd only do the fromdigits conversion once if that made sense.
Looking at performance:
Rate base36__A base36__B base____B base____A ntheory_A ntheory_B base36__A 0.168/s -- -42% -99% -99% -100% -100% base36__B 0.290/s 73% -- -99% -99% -100% -100% base____B 22.1/s 13090% 7522% -- -16% -91% -94% base____A 26.4/s 15672% 9014% 20% -- -89% -93% ntheory_A 238/s 141957% 81993% 977% 801% -- -34% ntheory_B 361/s 215202% 124321% 1532% 1265% 52% --Math::Base36 is quite slow, though if you're only doing a few calls (vs. 10k) it won't matter. Math::Base is actually quite fast for being all Perl. All of them will benefit if you can convert to decimal, do a bunch of calculations with that native form, then turn it back. Math::Base gives you the interesting alternative of doing a bunch of calculations directly in the base, only converting when needed.I believe the old Math::Fleximal (written as part of a perlmonks discussion) also does this. An aside that Perl6 for bases up to 36 is easy, intuitive, and all built-in.
#!usr/bin/env perl use warnings; use strict; use Benchmark qw/cmpthese/; use ntheory qw/todigitstring fromdigits/; use Math::Base36 qw/encode_base36 decode_base36/; require "./mathbase.pm"; sub ntheoryA { my $v = shift; $v = todigitstring(fromdigits($v,36)+1,36) for 1..10000; $v; } sub ntheoryB { my $v = shift; my $n = fromdigits($v,36); $v = todigitstring(++$n,36) for 1..10000; $v; } sub base36A { my $v = shift; $v = lc encode_base36(decode_base36($v)+1) for 1..10000; $v; } sub base36B { my $v = shift; my $n = decode_base36($v); $v = lc encode_base36(++$n) for 1..10000; $v; } sub baseA { my $v = shift; my $o = Math::Base->new(36,uc $v,1); $v = lc ++$o for 1..10000; $v; } sub baseB { my $v = shift; my $n = Math::Base->new(36,uc $v,1)->num; $v = lc Math::Base->new(36,++$n) for 1..10000; $v; } { # Check not obviously broken. die "ntheoryA" unless ntheoryA('x000') eq 'x7ps'; die "ntheoryB" unless ntheoryB('x000') eq 'x7ps'; die "base36A" unless base36A('x000') eq 'x7ps'; die "base36B" unless base36A('x000') eq 'x7ps'; die "baseA" unless baseA('x000') eq 'x7ps'; die "baseB" unless baseB('x000') eq 'x7ps'; } cmpthese -5, { ntheory_A => sub { ntheoryA("0000"); }, ntheory_B => sub { ntheoryB("0000"); }, base36__A => sub { base36A("0000"); }, base36__B => sub { base36B("0000"); }, base____A => sub { baseA("0000"); }, base____B => sub { baseB("0000"); }, };
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