Reputation: 63

Match regex with numeric value and decimal

I need to match regex to value that is numeric with decimal. Currently I have /^-?[0-9]\d*(.\d+)/ but it does not account for .00 How would I fix that

Current Valid:

Current Invalid:

Alpha Character

Upvotes: 5

Answers (7)

JanLeeYu

Reputation: 1001

This might help. :

(^-?[\d+]*[\.\d+]*)

Just try :)

Upvotes: 0

Cary Swoveland

Reputation: 110755

Here's a different approach.

def match_it(str)
  str if str.gsub(/[\d\.-]/, '').empty? && Float(str) rescue nil
end

match_it "1"     #=> "1" 
match_it "1.0"   #=> "1.0" 
match_it "-1.0"  #=> "-1.0" 
match_it "1.33"  #=> "1.33" 
match_it ".00"   #=> ".00" 
match_it "-.00"  #=> "-.00" 
match_it "1.1e3" #=> nil 
match_it "Hi!"   #=> nil

Upvotes: 0

Pedro Lobito

Reputation: 99061

Create a regex with the variants you want to match, in this case, 3:

N
N.NN
.NN

i.e.:

(\d+\.\d+|\d+|\.\d+)

regex 101 Demo

Upvotes: 1

Awesominator

Reputation: 130

I would use something like ^\-?[0-9\.]+ or (^\-?[0-9\.]+), if you want to capture that specific part of the line only. This looks for any combination of the digits 0 through 9 and a decimal point (.), at the beginning of a line with the option of it starting with a dash (-).

I also highly recommend the website Rubular as a great place to test and play with regexes.

Upvotes: 0

Casimir et Hippolyte

Reputation: 89639

You need to handle the two possibilities (numbers without a decimal part and numbers without an integer part):

/\A-?(?:\d+(?:\.\d*)?|\.\d+)\z/
#^   ^  ^            ^^     ^---- end of the string
#|   |  |            |'---- without integer part
#|   |  |            '---- OR
#|   |  '---- with an optional decimal part
#|   '---- non-capturing group
#'---- start of the string

or make all optional and ensure there's at least one digit:

/\A-?+(?=.??\d)\d*\.?\d*\z/
#  ^  ^  ^        ^---- optional dot
#  |  |  '---- optional char (non-greedy)
#  |  '---- lookahead assertion: means "this position is followed by"
#  '---- optional "-" (possessive)

Note: I used the non-greedy quantifier ?? only because I believe that numbers with integer part are more frequent, but it can be a false assumption. In this case change it to a greedy quantifier ?. (whatever the kind of quantifier you use for the "unknow char" it doesn't matter, this will not change the result.)

Upvotes: 6