RegEx question: Phrases starting with a small letter only

[BlackCanopus]

Hi

I am new to RegEx, but I want to use 'Tag mapper' and RegEx to put my tags in order (I imagine you are already cursing me ).

I want to capitalize all the tags that begin with a small letter.
My ideal conversion is "this test" -> "This Test" but I think it cannot be. So, "this test" to "This test" will also do.

I tried this:
Tage mapper > Capitalize the tag, if it matches pattern:

^[a-z].+?$

It capitalizes phrases such as:

this test

but it also capitalizes phrases such as

John Milton

and converts it to

John milton

I don't want that to happen. This phrase is already capitalized, it does not beging with a small letter, why does the RegEx statement validate it?

It seems I'm doing something wrong. Your help would be appreciated.

[kovidgoyal]

iirc the regex is treated as case-insensitive which is why a-z matches upper case letters as well.

[BlackCanopus]

Originally Posted by kovidgoyal

iirc the regex is treated as case-insensitive which is why a-z matches upper case letters as well.

RegEx cheat-sheets that I have say that it should be case-sensitive and i is used for making it case-insensitive.

Example:
https://www.rexegg.com/regex-modifiers.html

I searched StackOverflow but all of the questions were about how to make RegEx case-insensitive.

Perhaps the RegEx engine that Calibre uses is case-insensitive? But if so, is there a way to make it case-sensitive?


=== EDIT ===
This text has been quoted from the link above:

For several engines, note that there are two ways of turning on case-insensitive matching: as an inline modifier (?i) or as an option in the regex method or function.

Inline Modifier (?i)
In .NET, PCRE (C, PHP, R…), Perl, Python, Java and Ruby (but not JavaScript), you can use the inline modifier (?i), for instance in (?i)cat. See the section on inline modifiers for juicy details about three additional features (unavailable in Python): turning it on in mid-string, turning it off with (?-i), or applying it only to the content of a non-capture group with (?i:foo)

.NET
Apart from the (?i) inline modifier, .NET languages have the IgnoreCase option. For instance, in C# you can use:

var catRegex = new Regex("cat", RegexOptions.IgnoreCase);

Perl
Apart from the (?i) inline modifier, Perl lets you add the i flag after your pattern's closing delimiter. For instance, you can use:

if ($the_subject =~ m/cat/i) { … }

PCRE (C, PHP, R…)
Note that in PCRE, to use case-insensitive matching with non-English letters that aren't part of your locale, you'll have to turn on Unicode mode—for instance with the (*UTF8) special start-of-pattern modifier.

Apart from the (?i) inline modifier, PCRE lets you set the PCRE_CASELESS mode when calling the pcre_compile() (or similar) function:

cat_regex = pcre_compile( "cat", PCRE_CASELESS,
&error, &erroroffset, NULL );

Perhaps in the Calibre code, RegEx function has been called with case-insensitive command option? If yes, would it be possible to turn it off, please? :P

[BetterRed]

Elsewhere in calibre Title Case ups first char in each word, Capitalise only ups the first char in first word.

FX right click Series Name cell, select Change Case->Title Case will change dog's breakfast to Dog's Breakfast whereas Change Case->Capitalise will change it to Dog's breakfast.

Seems a bit odd the Tag Mapper does not offer Titlecase.

BR

[kovidgoyal]

It is case-insensitive deliberately, i/e/ the ignore case flag is passed by default. You can turn it off IIRC by prefixing with a minus, something like this:

(?-i:...)

see https://pypi.python.org/pypi/regex

[BlackCanopus]

Originally Posted by BetterRed

Elsewhere in calibre Title Case ups first char in each word, Capitalise only ups the first char in first word.

FX right click Series Name cell, select Change Case->Title Case will change dog's breakfast to Dog's Breakfast whereas Change Case->Capitalise will change it to Dog's breakfast.

Seems a bit odd the Tag Mapper does not offer Titlecase.

BR

This (adding 'Title Case' to 'Tag mapper') is a good solution.

It is case-insensitive deliberately, i/e/ the ignore case flag is passed by default. You can turn it off IIRC by prefixing with a minus, something like this:

(?-i:...)

see https://pypi.python.org/pypi/regex

Sadly I couldn't find it, but what BetterRed said is better. Would you please add Title Case to Tag Mapper?

[kovidgoyal]

I dont really see the point, tags are not titles, so why would title case be appropriate for them? You want to turn off case insensitivity, do it like I showed you

(?-i:^[a-z].+?$)

[BlackCanopus]

Originally Posted by kovidgoyal

I dont really see the point, tags are not titles, so why would title case be appropriate for them? You want to turn off case insensitivity, do it like I showed you

(?-i:^[a-z].+?$)

The code you gave doesn't work. But it doesn't matter anymore, I will find another solution. Thanks anyway.

As for the reason (for those who may be interested), titles such as John Milton, James Joyce, etc. may be used as tags. Note that these are not author names, but tags for books about those authors. This is used in literary criticism, I can imagine many other scenarios that use titles as tags. For example:

Title:	Novel Destinations, 2nd Edition
Authors:	Shannon McKenna Schmidt & Joni Rendon
Tags:	Charlotte Bronte, Emily Bronte, Ernest Hemingway, Fiction, Jack Kerouac, James Joyce, Jane Austen, Kafka, Literary Criticism & Collections, Literary Studies, Louisa May Alcott, Mark Twain, Novel, Virginia Woolf
Published:	May 2017
Publisher:	National Geographic Society

[theducks]

Originally Posted by kovidgoyal

I dont really see the point, tags are not titles, so why would title case be appropriate for them?

I treat/use Tags as Keywords (What coding I used to do, I used CamelCase for builtin functions)

some folk only use lowercase, others the hated (shouting) Uppercase
there will always be the rule busters: LITRPG, SF... that need TLC

[BetterRed]

Another case for using titlecase on Tags is place names - New York, West Australia, Tunbridge Wells etc. Novels are often just as much about places as they are about people.

BR