Help understanding Luau string patterns

[WithEnemy (Enemy)]

I’m trying to learn how to use Luau string patterns in Roblox studio.
I’ve been looking on the Roblox documentation about it, but it’s really confusing. I understand the simple “%d+” and etc, but I don’t understand further down the documentation where they start using “?,-,()”.
I’ve looked a little on the developer forum, but all solutions basically tell you to go back to the Roblox documentation.

If somebody has a larger explanation/understanding of this, I really appreciate the help.

[Artzified]

theres probably a better way to explain it but,
lets say you want to get all numbers in a string

local str = "1+1=11?"

for number in str:gmatch("%d+") do
   print(number) -- 1, 1, 11
end

for number in str:gmatch("%d") do
   print(number) -- 1, 1, 1, 1 (get individual numbers)
end

print( str:gsub("%d+") ) -- +=? (removes the numbers)

gmatch is a function that returns an iterator function which then you can get all the matches. and gsub removes all the matches in a string.

%d means, hey get all the numbers in this string!, and the + which is the quantifier, determines do i get more than 1 or just 1?

for the ? quantifier, it means get 0 or more characters, for example string.match("This is a RANDom string", "%a?") returns “RAND”

more information here: Strings | Documentation - Roblox Creator Hub

[WithEnemy (Enemy)]

Thank you for responding so quick!

But the problem is that I don’t really understand these types of patterns: “(%a+)%s?=%s?(%d+)”.

[Artzified]

ok lets break it down,

@WithEnemy

“(%a+)%s?=%s?(%d+)”.

first, we have 2 capturing groups, which is what is returned,

the first one is %a+, which means “An uppercase or lowercase letter”. and the quantifier is +, which means get 1 OR more characters

which is followed by %s?, which is “A space or whitespace character”. which has the ? quantifier, which means get 1 OR less characters

the second capturing group is %d+, which means “Any digit (number)” and followed by the + quantifier

the capturing groups, is what the function returns, in this case it returns the %a+ and the %d+

when we run that pattern in a match function

local str, num = string.match("HelloWorld = 5", "(%a+)%s?=%s?(%d+)")

print(str, num) -- HelloWorld 5

this also matches with:

• HelloWorld = 5
• HelloWorld=5
• HelloWorld= 5
• HelloWorld=59
• etc…

[WithEnemy (Enemy)]

Ohhh, I kinda understand now. But what does the %s?=%s? do?

[Artzified]

sorry, i mistaken the ? quantifier with *, ? means 1 OR less characters, while * means 0 OR more characters. the %s?=%s? means, is there one or no whitespace between = ?

so these would not match %s?=%s?

"  = " -- two spaces, invalid!
"=   " -- three spaces, invalid!

string patterns seems hard at first, but once you get the hang of it, its gonna make your scripting much easier

[WithEnemy (Enemy)]

OH, Thank you so much! I’ll start using string patterns more!

[mattozzo]

My question is unrelated, but what is the usage of the - modifier? Because I played around with it a little and it seems to be useless.

[Artzified]

I’m not sure about that, I’ve never practically used it (as a quantifier), but it really seems to be useless, because it will get no matches, but you can try doing [A-Z] (matches all characters from A to Z), which uses -, but not in a “quantifier” way