Help!!! LUA: how to know if a string contains substring with special symbols?

[kartalex]

Hi, all!

why this code:

p="PS02 - Fretted stereo2stereo (x86)"
s="PS02 - "
if string.match(p,s) then
reaper.ShowConsoleMsg("Yes!")
end

gives us "Yes!"

But this Code:

-- ex
p="PS02 - Fretted stereo2stereo (x86)"
s="PS02 - F"
if string.match(p,s) then
reaper.ShowConsoleMsg("Yes!")
end

gives us nothing??

How to know if some string contain another (with whitespaces or another symbols like "-" or "()" ???

[cfillion]

The dash is a metacharacter that matches the previous character class zero or more times (non-greedily). You can escape it (and any other Lua pattern special characters) by prefixing with a % character.

https://www.lua.org/manual/5.3/manual.html#6.4.1

("PS02 - Fretted stereo2stereo (x86)"):match("PS02 - F") matches PS02 followed by zero or more spaces, a space then an F.
("PS02 - Fretted stereo2stereo (x86)"):match("PS02 %- F") matches PS02 followed by a space, a dash, a space and an F.
("PS02 - Fretted stereo2stereo (x86)"):find("PS02 - F", 1, true) does the same as the above. find's third argument enables plain text mode.

[kartalex]

Originally Posted by cfillion

The dash is a metacharacter that matches the previous character class zero or more times (non-greedily). You can escape it (and any other Lua pattern special characters) by prefixing with a % character.

https://www.lua.org/manual/5.3/manual.html#6.4.1

("PS02 - Fretted stereo2stereo (x86)"):match("PS02 - F") matches PS02 followed by zero or more spaces, a space then an F.
("PS02 - Fretted stereo2stereo (x86)"):match("PS02 %- F") matches PS02 followed by a space, a dash, a space and an F.
("PS02 - Fretted stereo2stereo (x86)"):find("PS02 - F", 1, true) does the same as the above. find's third argument enables plain text mode.

Yes! It works!!
Thank you! I've spent the whole night, trying to find out how to do it!

[Meo-Ada Mespotine]

Just in case you don't know of it, but there's a reference-manual for Lua as well:

https://www.lua.org/manual/5.3/manual.html#6.4.1

%x: (where x is any non-alphanumeric character) represents the character x. This is the standard way to escape the magic characters. Any non-alphanumeric character (including all punctuation characters, even the non-magical) can be preceded by a '%' when used to represent itself in a pattern.

Means, such characters are called "magic characters" in Lua. There's a list in that chapter of all magic characters, that you might want to search for as well, that could do special stuff.
If you don't want them to do anything special, the % before them escapes them quite good.

[kartalex]

Originally Posted by mespotine

Means, such characters are called "magic characters" in Lua. There's a list in that chapter of all magic characters, that you might want to search for as well, that could do special stuff.
If you don't want them to do anything special, the % before them escapes them quite good.

Yes, now I understand how it works, thanks!