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Perl, 119 bytes Read a single Roman numeral on stdin (optionally newline-terminated). Outputs nothing unless one of the 50 strings is found, in which case it is printed (without trailing newline):...
#5: Post edited
by
jhnc
·
2026-03-09T17:01:43Z (6 months ago)
optimise regex
Perl, 125 bytes- ---
- Read a single Roman numeral on stdin (optionally newline-terminated). Outputs nothing unless one of the 50 strings is found, in which case it is printed (without trailing newline):
- ```
perl -pe'($_)=/CCCC|C[CM][DM]|C[DM]C|IIII|I[IX][VX]|I[VX]I|MMMM|VI?[VX]|XC[CLX]|XLX|XXXX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]/g'- ```
- Minimising a regex is nontrivial but will probably be the bulk of any solution. I expect it is possible to shrink it even more than this attempt.
- * `-p` - load each line of input as `$_`, manipulate, then print
- * `-e` - program follows
- * `/.../g` - return list of all matches
- * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string)
To read a newline-separated list of numerals and to print "VALID" instead of nothing increases code to 132 bytes:- ```
perl -ple'$_=/CCCC|C[CM][DM]|C[DM]C|IIII|I[IX][VX]|I[VX]I|MMMM|VI?[VX]|XC[CLX]|XLX|XXXX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID'- ```
- * `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`
[Try it online!][TIO-mmdmcwbq][TIO-mmdmcwbq]: https://tio.run/##LVLBitswFLzrKx67obm02VMvW0oo0kWgdxUPjNl4HW3iJrGMpTQU/O1NR8oKniXNmxmNhKcwn7/fn8nSPo7rTKcx3uiIypEOIVM@Dqmsu74PU6bLX@rjPtB17I/deAh79Uwpkl3/CRTGHOawhyTQLqxXbz83m816R1M3Z@oS/b6mTLsHvKNhrMTqlkKfhzjSezjHm4LlR5wph5SH8fD1EeE8jKHAly6nKozXPF1ziXaO8UQdvQ8ZrFOo3SKmvkshwa2PlwvCEQhQVfO5u9Ec0vWck5rmYcwf9LR6o1d6@nFHwheNsehGc9sYbrHCVy8WY7GNlbbx0mKFr10YY/F2WzGByJXZySIYS2Ok1dvq0ljn20Yb91hLK@C2L9vVl1f/y1lzv1vllSintDKKlcUWewBAAAErIFCU9Sjr0bCoMguqEDXKoCrXKnYGHxEYaGtFsS65MGEITJid6OKIa2gWXSjMBl0Hnq8WhSzOq0qoGjGfDQPFJ4UN@KqYa@dEYWeYSzJjjGXE906L9cLai0Mc7yxeBCHEsyt3xcvgWjjWQF0ic@mzc8UFR0IPL4e31QoBRJcOQK53Bd9gVzQ4yxiuEHIZzfwvTuUXS/dv0/k/ "Perl 5 – Try It Online"
- Perl, 119 bytes
- ---
- Read a single Roman numeral on stdin (optionally newline-terminated). Outputs nothing unless one of the 50 strings is found, in which case it is printed (without trailing newline):
- ```
- perl -pe'($_)=/([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]/g'
- ```
- Minimising a regex is nontrivial but will probably be the bulk of any solution. I expect it is possible to shrink it even more than this attempt.
- * `-p` - load each line of input as `$_`, manipulate, then print
- * `-e` - program follows
- * `/.../g` - return list of all matches
- * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string)
- To read a newline-separated list of numerals and to print "VALID" instead of nothing increases code to 126 bytes:
- ```
- perl -ple'$_=/([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID'
- ```
- * `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`
- [Try it online!][TIO-mmjfcy6i]
- [TIO-mmjfcy6i]: https://tio.run/##XVTRahsxEHy/r1iSULfFsSmlLwltKNKLQHoVC9cjvpyVxI19Z3xyQ6n763Vmdc5F1GDdnDwzmtUu3obd@svxnAwtu3YS6antnukR39jRQ4gUH1e94LppwjbS5jc13TLQvm0e6/YhLItz6jsyk1@BQhvDLiwhCbQIk4vbr7PZbLKgbb2LVPf0c99HWgzbC1q1iZjc@tDEVdfSXVh3zwUs77sdxdDHVfswHSKsV22Q7U0d@yTs9nG7jxJt3XVPVNPdKoL1FNKvIqam7kMPt6bbbBCOQIAqme/qZ9qFfr@OfbHdrdp4T2cXt3T5jc6ui35OV7OP8/n1EWHn70tlHFcffnz68/nvQZXKVaV2FRBWdTCl4ar0XAFhNQdvbtIrg2rlaflQaq7UTZKVxvqqVNoOmCsGrZrfXLy78t@t0cejoStKsPAj4hHZEakR6RG5EZnMJvn4gjMXsbG2UJmJuGhY5B6ZSYaNF4wVDPHGCqe335XyGeYMZ@mzo5WSs7ECuYScnJ0OwadwVgu2CMcsMqyFVsZwYnDhFHOqTh54w4dTRkGoyLIa8gPg1SnHyrzlwo4G0ULs85qdOLF9KyYJfU5gPQg4sTVs/9M7DdOhpinhreCsDcpaHhoBlnZOiBo8TneitXGnrkzJiBw35K1i49kpzzbdIE/J2ylZBZkrtLcGE4by2TtrMoLB18PEKwwExg/tQ8E6hfHY1gOF8bSgSXe1XLcTO2ftGE5YVszUwAQHC1qGy8HxEtxi6NUp@BgOGNtT6UEqRZAtcIGsxB1Kl7qf0mQiOSslSjqXDrOYD5yroZJ84y29al@rGfOBPZVREbHMukt69EerNPAi1u7kj61cplPr9FDlKbpM3b9uK39b/fFyu34B "Perl 5 – Try It Online"
#4: Post edited
by
jhnc
·
2026-03-05T15:28:58Z (7 months ago)
smaller regex; only accept single numeral
Perl, 135 bytes- ---
Takes newline-separated list of Roman numerals as input. Outputs nothing unless one of the 50 strings is found, in which case it is printed:- ```
perl -ple'($_)=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/g'- ```
Minimising a regex is nontrivial but seems to be the bulk of any code. I expect it is possible to shrink it even more than this attempt.* `-l` - strip newline from input and add it back on output- * `-p` - load each line of input as `$_`, manipulate, then print
- * `-e` - program follows
- * `/.../g` - return list of all matches
- * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string)
To print "VALID" instead of nothing increases code to 141 bytes:- ```
perl -ple'$_=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID'- ```
- * `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`
[Try it online!][TIO-mmdh20oa][TIO-mmdh20oa]: https://tio.run/##LVLBitswEL3rK4bd0Fza7KmXLWUp0kUgXcWAMRuvo03cOJaxlC4Ff3vTN8oOjDWaee/pSXiOy/j99kiWDmnaFjpP6YNOyJLoGAuV05Cl7vo@zoUuf6lPh0jXqT910zEe1CPlRHb7J1KcSlziAZRI@7jdvP7c7XbbPc3dUqjL9PuaC@3v7T0NUwVWtRz7MqSJ3uKYPhQk39NCJeYyTMevdwvjMEVpX7qSKzFdy3wtYm1M6UwdvQ0FqHOsUyFT3@WYodanywXmCACwqvjSfdAS83UsWc3LMJV3eti80jM9/LjB4ZNGrBaxesTKiFUbvWrfaOPb1TaW2yawVPjaNdR1DfXLutFOVscr8NzqRkgNqnthXWgxcPeaWwa@fXrZfHkOv5w1t5tVQbFySiujvLLYYo8GOmihJ010kTYgbcDAImVlpAA10iAr1irvDD7MENDWsvJaroUFwRDx3rEWRdxYe9YC8d5g6oALVULA7IKqgMph8zkwYHxCvAFeibh2jhV2xntxZoyxHvaD02wDex3YwU5wFi8CExy8k7viZXAtHGvAFste5t45UcGR4EPL4X21ggHWMkHT17sCb7ATDs4yxtcWfBnt/b80y7@Wb9/m8T8 "Perl 5 – Try It Online"
- Perl, 125 bytes
- ---
- Read a single Roman numeral on stdin (optionally newline-terminated). Outputs nothing unless one of the 50 strings is found, in which case it is printed (without trailing newline):
- ```
- perl -pe'($_)=/CCCC|C[CM][DM]|C[DM]C|IIII|I[IX][VX]|I[VX]I|MMMM|VI?[VX]|XC[CLX]|XLX|XXXX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]/g'
- ```
- Minimising a regex is nontrivial but will probably be the bulk of any solution. I expect it is possible to shrink it even more than this attempt.
- * `-p` - load each line of input as `$_`, manipulate, then print
- * `-e` - program follows
- * `/.../g` - return list of all matches
- * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string)
- To read a newline-separated list of numerals and to print "VALID" instead of nothing increases code to 132 bytes:
- ```
- perl -ple'$_=/CCCC|C[CM][DM]|C[DM]C|IIII|I[IX][VX]|I[VX]I|MMMM|VI?[VX]|XC[CLX]|XLX|XXXX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID'
- ```
- * `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`
- [Try it online!][TIO-mmdmcwbq]
- [TIO-mmdmcwbq]: https://tio.run/##LVLBitswFLzrKx67obm02VMvW0oo0kWgdxUPjNl4HW3iJrGMpTQU/O1NR8oKniXNmxmNhKcwn7/fn8nSPo7rTKcx3uiIypEOIVM@Dqmsu74PU6bLX@rjPtB17I/deAh79Uwpkl3/CRTGHOawhyTQLqxXbz83m816R1M3Z@oS/b6mTLsHvKNhrMTqlkKfhzjSezjHm4LlR5wph5SH8fD1EeE8jKHAly6nKozXPF1ziXaO8UQdvQ8ZrFOo3SKmvkshwa2PlwvCEQhQVfO5u9Ec0vWck5rmYcwf9LR6o1d6@nFHwheNsehGc9sYbrHCVy8WY7GNlbbx0mKFr10YY/F2WzGByJXZySIYS2Ok1dvq0ljn20Yb91hLK@C2L9vVl1f/y1lzv1vllSintDKKlcUWewBAAAErIFCU9Sjr0bCoMguqEDXKoCrXKnYGHxEYaGtFsS65MGEITJid6OKIa2gWXSjMBl0Hnq8WhSzOq0qoGjGfDQPFJ4UN@KqYa@dEYWeYSzJjjGXE906L9cLai0Mc7yxeBCHEsyt3xcvgWjjWQF0ic@mzc8UFR0IPL4e31QoBRJcOQK53Bd9gVzQ4yxiuEHIZzfwvTuUXS/dv0/k/ "Perl 5 – Try It Online"
#3: Post edited
by
jhnc
·
2026-03-05T13:09:42Z (7 months ago)
link to tio
- Perl, 135 bytes
- ---
- Takes newline-separated list of Roman numerals as input. Outputs nothing unless one of the 50 strings is found, in which case it is printed:
- ```
- perl -ple'($_)=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/g'
- ```
- Minimising a regex is nontrivial but seems to be the bulk of any code. I expect it is possible to shrink it even more than this attempt.
- * `-l` - strip newline from input and add it back on output
- * `-p` - load each line of input as `$_`, manipulate, then print
- * `-e` - program follows
- * `/.../g` - return list of all matches
- * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string)
- To print "VALID" instead of nothing increases code to 141 bytes:
- ```
- perl -ple'$_=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID'
- ```
- * `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`
- [Try it online!][TIO-mmdh20oa]
[Perl 5]: https://www.perl.org/[TIO-mmdh20oa]: https://tio.run/##LVBNi9tADL3Prxjo0lza7KmXQilFugik6yAwpkmTYbNtapvY26Uwv73uk7MCjaSnp6@Z6u36aX2XJZ/HYbfkX8P4mi/QZcxPdcnL5XkO/3g61WnJv//m03iu@WU4XY7DUz1/yPOYZfen5jos9VbPqKj5UHcP37/s9/vdIU/H25KPc/75Mi/5cIcP@Ue9jq8rokeCNIE0gzSHNGJqZB2x9U068b4rHh5eaWWzrWyvU0caVr2B7z11UdTBuzuipUdC7773Dn7/@PXh/efyTYXXVVJJnjRR4mRJECIGAAQQsACBQqVApSAh0LAODSJBGbpxJZkyHnc0IBFPRnEWDMTRxEydoiMuJnMKihkjq@CVrUWQXUvaCFuN81uCUfFGMQY/RXNS9YSIzWIzZhbD@kXJpbhRccU6RQU/giW8mMat@BmchbGM6ljZIm@q0QUjUY9eiv@lhAWcIgPQtlvBZ0RRg1nMtkHYi8ns3zgtz@Mwrx@n638 "Perl 5 – Try It Online"
- Perl, 135 bytes
- ---
- Takes newline-separated list of Roman numerals as input. Outputs nothing unless one of the 50 strings is found, in which case it is printed:
- ```
- perl -ple'($_)=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/g'
- ```
- Minimising a regex is nontrivial but seems to be the bulk of any code. I expect it is possible to shrink it even more than this attempt.
- * `-l` - strip newline from input and add it back on output
- * `-p` - load each line of input as `$_`, manipulate, then print
- * `-e` - program follows
- * `/.../g` - return list of all matches
- * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string)
- To print "VALID" instead of nothing increases code to 141 bytes:
- ```
- perl -ple'$_=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID'
- ```
- * `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`
- [Try it online!][TIO-mmdh20oa]
- [TIO-mmdh20oa]: https://tio.run/##LVLBitswEL3rK4bd0Fza7KmXLWUp0kUgXcWAMRuvo03cOJaxlC4Ff3vTN8oOjDWaee/pSXiOy/j99kiWDmnaFjpP6YNOyJLoGAuV05Cl7vo@zoUuf6lPh0jXqT910zEe1CPlRHb7J1KcSlziAZRI@7jdvP7c7XbbPc3dUqjL9PuaC@3v7T0NUwVWtRz7MqSJ3uKYPhQk39NCJeYyTMevdwvjMEVpX7qSKzFdy3wtYm1M6UwdvQ0FqHOsUyFT3@WYodanywXmCACwqvjSfdAS83UsWc3LMJV3eti80jM9/LjB4ZNGrBaxesTKiFUbvWrfaOPb1TaW2yawVPjaNdR1DfXLutFOVscr8NzqRkgNqnthXWgxcPeaWwa@fXrZfHkOv5w1t5tVQbFySiujvLLYYo8GOmihJ010kTYgbcDAImVlpAA10iAr1irvDD7MENDWsvJaroUFwRDx3rEWRdxYe9YC8d5g6oALVULA7IKqgMph8zkwYHxCvAFeibh2jhV2xntxZoyxHvaD02wDex3YwU5wFi8CExy8k7viZXAtHGvAFste5t45UcGR4EPL4X21ggHWMkHT17sCb7ATDs4yxtcWfBnt/b80y7@Wb9/m8T8 "Perl 5 – Try It Online"
#2: Post edited
by
jhnc
·
2026-03-05T13:00:52Z (7 months ago)
link to tio
- Perl, 135 bytes
- ---
- Takes newline-separated list of Roman numerals as input. Outputs nothing unless one of the 50 strings is found, in which case it is printed:
- ```
- perl -ple'($_)=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/g'
- ```
- Minimising a regex is nontrivial but seems to be the bulk of any code. I expect it is possible to shrink it even more than this attempt.
- * `-l` - strip newline from input and add it back on output
- * `-p` - load each line of input as `$_`, manipulate, then print
- * `-e` - program follows
- * `/.../g` - return list of all matches
- * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string)
- To print "VALID" instead of nothing increases code to 141 bytes:
- ```
- perl -ple'$_=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID'
- ```
* `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`
- Perl, 135 bytes
- ---
- Takes newline-separated list of Roman numerals as input. Outputs nothing unless one of the 50 strings is found, in which case it is printed:
- ```
- perl -ple'($_)=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/g'
- ```
- Minimising a regex is nontrivial but seems to be the bulk of any code. I expect it is possible to shrink it even more than this attempt.
- * `-l` - strip newline from input and add it back on output
- * `-p` - load each line of input as `$_`, manipulate, then print
- * `-e` - program follows
- * `/.../g` - return list of all matches
- * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string)
- To print "VALID" instead of nothing increases code to 141 bytes:
- ```
- perl -ple'$_=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID'
- ```
- * `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`
- [Try it online!][TIO-mmdh20oa]
- [Perl 5]: https://www.perl.org/
- [TIO-mmdh20oa]: https://tio.run/##LVBNi9tADL3Prxjo0lza7KmXQilFugik6yAwpkmTYbNtapvY26Uwv73uk7MCjaSnp6@Z6u36aX2XJZ/HYbfkX8P4mi/QZcxPdcnL5XkO/3g61WnJv//m03iu@WU4XY7DUz1/yPOYZfen5jos9VbPqKj5UHcP37/s9/vdIU/H25KPc/75Mi/5cIcP@Ue9jq8rokeCNIE0gzSHNGJqZB2x9U068b4rHh5eaWWzrWyvU0caVr2B7z11UdTBuzuipUdC7773Dn7/@PXh/efyTYXXVVJJnjRR4mRJECIGAAQQsACBQqVApSAh0LAODSJBGbpxJZkyHnc0IBFPRnEWDMTRxEydoiMuJnMKihkjq@CVrUWQXUvaCFuN81uCUfFGMQY/RXNS9YSIzWIzZhbD@kXJpbhRccU6RQU/giW8mMat@BmchbGM6ljZIm@q0QUjUY9eiv@lhAWcIgPQtlvBZ0RRg1nMtkHYi8ns3zgtz@Mwrx@n638 "Perl 5 – Try It Online"
#1: Initial revision
by
jhnc
·
2026-03-05T04:35:49Z (7 months ago)
Perl, 135 bytes --- Takes newline-separated list of Roman numerals as input. Outputs nothing unless one of the 50 strings is found, in which case it is printed: ``` perl -ple'($_)=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/g' ``` Minimising a regex is nontrivial but seems to be the bulk of any code. I expect it is possible to shrink it even more than this attempt. * `-l` - strip newline from input and add it back on output * `-p` - load each line of input as `$_`, manipulate, then print * `-e` - program follows * `/.../g` - return list of all matches * `($_) = ...` - store first match in `$_` (if no matches, assigns empty string) To print "VALID" instead of nothing increases code to 141 bytes: ``` perl -ple'$_=/CCCC|IIII|MMMM|XXXX|CDC|CM[CDM]|I[IX][VX]|I[VX]I|VI[VX]|V[VX]|XC[CLX]|XLX|[CDX]C[DM]|[DX][DM]|[ILV][CDLM]|[ILX]X[CL]/?$&:VALID' ``` * `$_ = /.../ ? $& : VALID` - ternary assignment to `$_` - if a match is found, assign its value (`$&`), otherwise assign bareword `VALID`