I have a string and I need to remove trailing zeros after the 2nd decimal place:
remove_zeros("1,2,3,4.2300") #=> "1,2,3,4.23"
remove_zeros("1,2,3,4.20300") #=> "1,2,3,4.203"
remove_zeros("1,2,3,4.0200") #=> "1,2,3,4.02"
remove_zeros("1,2,3,4.0000") #=> "1,2,3,4.00"
Missing zeros don't have to be appended, i.e.
remove_zeros("1,2,3,4.0") #=> "1,2,3,4.0"
How could I do this in Ruby? I tried with converting into Float but it terminates the string when I encounter a ,. Can I write any regular expression for this?
Yes, a regular expression could be used.
R = /
\. # match a decimal
\d*? # match one or more digits lazily
\K # forget all matches so far
0+ # match one or more zeroes
(?!\d) # do not match a digit (negative lookahead)
/x # free-spacing regex definition mode
def truncate_floats(str)
str.gsub(R,"")
end
truncate_floats "1,2,3,4.2300"
#=> "1,2,3,4.23"
truncate_floats "1.34000,2,3,4.23000"
#=> "1.34,2,3,4.23"
truncate_floats "1,2,3,4.23003500"
#=> "1,2,3,4.230035"
truncate_floats "1,2,3,4.3"
#=> "1,2,3,4.3"
truncate_floats "1,2,3,4.000"
#=> "1,2,3,4."
> a = "1,2,3,4.2300"
> a.split(",").map{|e| e.include?(".") ? e.to_f : e}.join(",")
#=> "1,2,3,4.23"
> a = "1,2,3,4.20300"
> a.split(",").map{|e| e.include?(".") ? e.to_f : e}.join(",")
#=> "1,2,3,4.203"
First, you need to parse the string into its component numbers, then remove the trailing zeros on each number. This can be done by:
1) splitting the string on ',' to get an array of numeric strings
2) for each numeric string, convert it to a Float, then back to a string:
#!/usr/bin/env ruby
def parse_and_trim(string)
number_strings = string.split(',')
number_strings.map { |s| Float(s).to_s }.join(',')
end
p parse_and_trim('1,2,3,4.2300') # => "1.0,2.0,3.0,4.23"
If you really want to remove the trailing '.0' fragments, you could replace the script with this one:
#!/usr/bin/env ruby
def parse_and_trim_2(string)
original_strings = string.split(',')
converted_strings = original_strings.map { |s| Float(s).to_s }
trimmed_strings = converted_strings.map do |s|
s.end_with?('.0') ? s[0..-3] : s
end
trimmed_strings.join(',')
end
p parse_and_trim_2('1,2,3,4.2300') # => "1,2,3,4.23"
These could of course be made more concise, but I've used intermediate variables to clarify what's going on.
Related
What is a good regex to match any namespaced Ruby Class or Module name?
More generally, how do I match sequences of words separated by double colons?
Word1::Word2
Word1::Word2::Word3
Word1::Word2::Word3::Word4
etc.
This is the closest thing I got, but it only works for up to two consecutive words:
string.scan /[a-zA-Z0-9]+(?:\:\:[a-zA-Z0-9]+)/
Your approach is fine you should only quantify capturing group or a shorter:
\b\w+(?:::\w+)+\b
Live demo
R = /
\A # match beginning of string
(?: # begin a non-capture group
(?:::)? # optionally match two colons
\p{Lu} # match an uppercase letter
\w* # match zero or more word characters
)+ # close non-capture group and execute group one or more times
\z # match end of string
/x # free-spacing regex definition mode
'AB::CD::EF'.match?(R) #=> true
'A'.match?(R) #=> true
'::A::C_d::E3F_'.match?(R) #=> true
'AB::cD::EF'.match?(R) #=> false
'AB:::CD::EF&'.match?(R) #=> false
Alternatively, we could write the following.
def valid_mod_name?(str)
i = str[0,2]=='::' ? 2 : 0
str[i..-1].split('::').all? { |s| s.match?(/\A\p{Lu}\w*\z/) }
end
valid_mod_name? 'AB::CD::EF' #=> true
valid_mod_name? 'A' #=> true
valid_mod_name? '::A::C_d::E3F_' #=> true
valid_mod_name? 'AB::cD::EF' #=> false
valid_mod_name? 'AB:::CD::EF&' #=> false
I've been attempting a coding exercise to mask all but the last four digits or characters of any input.
I think my solution works but it seems a bit clumsy. Does anyone have ideas about how to refactor it?
Here's my code:
def mask(string)
z = string.to_s.length
if z <= 4
return string
elsif z > 4
array = []
string1 = string.to_s.chars
string1[0..((z-1)-4)].each do |s|
array << "#"
end
array << string1[(z-4)..(z-1)]
puts array.join(", ").delete(", ").inspect
end
end
positive lookahead
A positive lookahead makes it pretty easy. If any character is followed by at least 4 characters, it gets replaced :
"654321".gsub(/.(?=.{4})/,'#')
# "##4321"
Here's a description of the regex :
r = /
. # Just one character
(?= # which must be followed by
.{4} # 4 characters
) #
/x # free-spacing mode, allows comments inside regex
Note that the regex only matches one character at a time, even though it needs to check up to 5 characters for each match :
"654321".scan(r)
# => ["6", "5"]
/(.)..../ wouldn't work, because it would consume 5 characters for each iteration :
"654321".scan(/(.)..../)
# => [["6"]]
"abcdefghij".scan(/(.)..../)
# => [["a"], ["f"]]
If you want to parametrize the length of the unmasked string, you can use variable interpolation :
all_but = 4
/.(?=.{#{all_but}})/
# => /.(?=.{4})/
Code
Packing it into a method, it becomes :
def mask(string, all_but = 4, char = '#')
string.gsub(/.(?=.{#{all_but}})/, char)
end
p mask('testabcdef')
# '######cdef'
p mask('1234')
# '1234'
p mask('123')
# '123'
p mask('x')
# 'x'
You could also adapt it for sentences :
def mask(string, all_but = 4, char = '#')
string.gsub(/\w(?=\w{#{all_but}})/, char)
end
p mask('It even works for multiple words')
# "It even #orks for ####iple #ords"
Some notes about your code
string.to_s
Naming things is very important in programming, especially in dynamic languages.
string.to_s
If string is indeed a string, there shouldn't be any reason to call to_s.
If string isn't a string, you should indeed call to_s before gsub but should also rename string to a better description :
object.to_s
array.to_s
whatever.to_s
join
puts array.join(", ").delete(", ").inspect
What do you want to do exactly? You could probably just use join :
[1,2,[3,4]].join(", ").delete(", ")
# "1234"
[1,2,[3,4]].join
# "1234"
delete
Note that .delete(", ") deletes every comma and every whitespace, in any order. It doesn't only delete ", " substrings :
",a b,,, cc".delete(', ')
# "abcc"
["1,2", "3,4"].join(', ').delete(', ')
# "1234"
Ruby makes this sort of thing pretty trivial:
class String
def asteriskify(tail = 4, char = '#')
if (length <= tail)
self
else
char * (length - tail) + self[-tail, tail]
end
end
end
Then you can apply it like this:
"moo".asteriskify
# => "moo"
"testing".asteriskify
# => "###ting"
"password".asteriskify(5, '*')
# => "***sword"
Try this one
def mask(string)
string[0..-5] = '#' * (string.length - 4)
string
end
mask("12345678")
=> "####5678"
I will add my solution to this topic too :)
def mask(str)
str.match(/(.*)(.{4})/)
'#' * ($1 || '').size + ($2 || str)
end
mask('abcdef') # => "##cdef"
mask('x') # => "x"
I offer this solution mainly to remind readers that String#gsub without a block returns an enumerator.
def mask(str, nbr_unmasked, mask_char)
str.gsub(/./).with_index { |s,i| i < str.size-nbr_unmasked ? mask_char : s }
end
mask("abcdef", 4, '#')
#=> "##cdef"
mask("abcdef", 99, '#')
#=> "######"
Try using tap
def mask_string(str)
str.tap { |p| p[0...-4] = '#' * (p[0...-4].length) } if str.length > 4
str
end
mask_string('ABCDEF') # => ##CDEF
mask_string('AA') # => AA
mask_string('S') # => 'S'
I have a sample string that I would like to transform, from this:
#21inch-#25inch
to this:
#21inch #22inch #23inch #24inch #25inch
Using Ruby, please show me how this can be done.
You can scan your string and working with range of strings:
numbers = "#21inch-#25inch".scan(/\d+/)
=> ["21", "25"]
Range.new(*numbers).map{ |s| "##{s}inch" }.join(" ")
=> "#21inch #22inch #23inch #24inch #25inch"
This solution working only if your string has a format like in your instance. For other cases you should write your own specific solution.
R = /
(\D*) # match zero or more non-digits in capture group 1
(\d+) # match one or more digits in capture group 2
([^\d-]+) # match on or more chars other the digits and hyphens in capture group 3
/x # free-spacing regex definition mode
def spin_out(str)
(prefix, first, units),(_, last, _) = str.scan(R)
(first..last).map { |s| "%s%s%s" % [prefix,s,units] }.join(' ')
end
spin_out "#21inch-#25inch"
#=> "#21inch #22inch #23inch #24inch #25inch"
spin_out "#45cm-#53cm"
#=> "#45cm #46cm #47cm #48cm #49cm #50cm #51cm #52cm #53cm"
spin_out "sz 45cm-sz 53cm"
#=> "sz 45cm sz 46cm sz 47cm sz 48cm sz 49cm sz 50cm sz 51cm sz 52cm sz 53cm"
spin_out "45cm-53cm"
#=> "45cm 46cm 47cm 48cm 49cm 50cm 51cm 52cm 53cm"
For str = "#21inch-#25inch", we obtain
(prefix, first, units),(_, last, _) = str.scan(R)
#=> [["#", "21", "inch"], ["-#", "25", "inch"]]
prefix
#=> "#"
first
#=> "21"
units
#=> "inch"
last
#=> "25"
The subsequent mapping is straightforward.
You can use a regex gsub with a block match replacement, like this:
string = "#21inch-#25inch"
new_string = string.gsub(/#\d+\w+-#\d+\w+/) do |match|
first_capture, last_capture = match.split("-")
first_num = first_capture.gsub(/\D+/, "").to_i
last_num = last_capture.gsub(/\D+/, "").to_i
pattern = first_capture.split(/\d+/)
(first_num..last_num).map {|num| pattern.join(num.to_s) }.join(" ")
end
puts "#{new_string}"
Running this will produce this output:
First: #21inch Last: #25inch
First num: 21 Last num: 25
Pattern: ["#", "inch"]
#21inch #22inch #23inch #24inch #25inch
The last line of output is the answer, and the previous lines show the progression of logic to get there.
This approach should work for other, slightly different unit formats, as well:
#32ft-#49ft
#1mm-5mm
#2acres-5acres
Making this suit multiple purposes will be quite simple. With a slight variation in the regex, you could also support a range format #21inch..#25inch:
/(#\d+\w+)[-.]+(#\d+\w+)/
Happy parsing!
I have this code:
str = 'printf("My name is %s and age is %0.2d", name, age);'
SPECIFIERS = 'diuXxofeEgsc'
format_specifiers = /((?:%(?:\*?([-+]?\d*\.?\d+)*(?:[#{SPECIFIERS}]))))/i
variables = /([.[^"]]*)\);$/
format = str.scan(format_specifiers)
var = str.scan(variables).first.first.split(/,/)
Is there any way a single regex can do that in a couple of lines?
My desired output is:
%s, name
%0.2d, age
I'm a big believer in keeping regular expressions as simple as possible; They can too quickly mushroom into unwieldy/unmaintainable messes. I'd start with something like this, then tweak as necessary:
str = 'printf("My name is %s and age is %0.2d", name, age);'
formats = str.scan(/%[a-z0-9.]+/) # => ["%s", "%0.2d"]
str[/,(.+)\);$/] # => ", name, age);"
vars = str[/,(.+)\);$/].scan(/[a-z]+/) # => ["name", "age"]
puts formats.zip(vars).map{ |a| a.join(', ')}
# >> %s, name
# >> %0.2d, age
Your question has two parts:
Q1: Is it possible to do this with a single regex?
Q2: Can this be done in one or two lines of code?
The answer to both questions is "yes".
format_specifiers = /
%[^\s\"\z]+ # match % followed by > 0 characters other than a
# whitespace, a double-quote or the end of the string
/x # free-spacing regex definition mode
variables = /
,\s* # match comma followed by >= 0 whitespaces
\K # forget matches so far
[a-z] # match a lowercase letter
\w* # match >= 0 word characters
/x
You can decide, after testing, if these two regexes do their jobs adequately. For testing, refer to Kernel#sprintf.
r = /
(?:#{format_specifiers}) # match format_specifiers in a non-capture group
| # or
(?:#{variables}) # match variables in a non-capture group
/x
#=> /
(?:(?x-mi:
%[^\s\"\z]+ # match % followed by > 0 characters other than a
# whitespace, a double-quote or the end of the string
)) # match format_specifiers in a non-capture group
| # or
(?:(?x-mi:
,\s* # match comma followed by >= 0 whitespaces
\K # forget matches so far
[a-zA-Z] # match a letter
\w* # match >= 0 word characters
)) # match variables in a non-capture group
/x
r can of course also be written:
/(?:(?x-mi:%[^\s\"\z]+))|(?:(?x-mi:,\s*\K[a-zA-Z]\w*))/
One advantage of constructing r from two regexes is that each of the latter can be tested separately.
str = 'printf("My name is %s and age is %0.2d", name, age);'
arr = str.scan(r)
#=> ["%s", "%0.2d", "name", "age"]
arr.each_slice(arr.size/2).to_a.transpose.map { |s| s.join(', ') }
#=> ["%s, name", "%0.2d, age"]
I have five lines of code. We could reduce this to two by simply substituting out r in str.scan(r). We could make it a single line by writing:
str.scan(r).tap { |a|
a.replace(a.each_slice(a.size/2).to_a.transpose.map { |s| s.join(', ') }) }
#=> ["%s, name", "%0.2d, age"]
with r substituted out.
The steps here are as follows:
a = str.scan(r)
#=> ["%s", "%0.2d", "name", "age"]
b = a.each_slice(a.size/2)
#=> a.each_slice(2)
#=> #<Enumerator: ["%s", "%0.2d", "name", "age"]:each_slice(2)>
c = b.to_a
#=> [["%s", "%0.2d"], ["name", "age"]]
d = c.transpose
#=> [["%s", "name"], ["%0.2d", "age"]]
e = d.map { |s| s.join(', ') }
#=> ["%s, name", "%0.2d, age"]
a.replace(e)
#=> ["%s, name", "%0.2d, age"]
The methods used (aside from Array#size) are String#scan, Enumerable#each_slice, Enumerable#to_a, Enumerable#map, Array#transpose and Array#replace.
I would like to verify a string containing repeated substrings. The substrings have a particular structure. Whole string has a particular structure (substring split by "|"). For instance, the string can be:
1=23.00|6=22.12|12=21.34|112=20.34
1=23.00|6=22.12|12=21.34
1=23.00|12=21.34
1=23.00**
How can I check that all repeated substrings match a regexp? I tried to check it with:
"1=23.00|6=22.12|12=21.34".match(/([1-9][0-9]*[=][0-9\.]+)+/)
But checking gives true even when several substrings do not match the regexp:
"1=23.00|6=ass|=21.34".match(/([1-9][0-9]*[=][0-9\.]+)+/)
# => #<MatchData "1=23.00" 1:"1=23.00">
The question is whether every repeated substring matches a regex. I understand that the substrings are separated by the character | or $/, the latter being the end of a line. We first need to obtain the repeated substrings:
a = str.split(/[#{$/}\|]/)
.map(&:strip)
.group_by {|s| s}
.select {|_,v| v.size > 1 }
.keys
Next we specify whatever regex you wish to use. I am assuming it is this:
REGEX = /[1-9][0-9]*=[1-9]+\.[0-9]+/
but it could be altered if you have other requirements.
As we wish to determine if all repeated substrings match the regex, that is simply:
a.all? {|s| s =~ REGEX}
Here are the calculations:
str =<<_
1=23.00|6=22.12|12=21.34|112=20.34
1=23.00|6=22.12|12=21.34
1=23.00|12=21.34
1=23.00**
_
c = str.split(/[#{$/}\|]/)
#=> ["1=23.00", "6=22.12", "12=21.34", "112=20.34", "1=23.00",
# "6=22.12", "12=21.34", "1=23.00", "12=21.34", "1=23.00**"]
d = c.map(&:strip)
# same as c, possibly not needed or not wanted
e = d.group_by {|s| s}
# => {"1=23.00" =>["1=23.00", "1=23.00", "1=23.00"],
# "6=22.12" =>["6=22.12", "6=22.12"],
# "12=21.34" =>["12=21.34", "12=21.34", "12=21.34"],
# "112=20.34"=>["112=20.34"], "1=23.00**"=>["1=23.00**"]}
f = e.select {|_,v| v.size > 1 }
#=> {"1=23.00"=>["1=23.00", "1=23.00" , "1=23.00"],
# "6=22.12"=>["6=22.12", "6=22.12"],
# "12=21.34"=>["12=21.34", "12=21.34", "12=21.34"]}
a = f.keys
#=> ["1=23.00", "6=22.12", "12=21.34"]
a.all? {|s| s =~ REGEX}
#=> true
This will return true if there are any duplicates, false if there are not:
s = "1=23.00|6=22.12|12=21.34|112=20.34|3=23.00"
arr = s.split(/\|/).map { |s| s.gsub(/\d=/, "") }
arr != arr.uniq # => true
If you want to resolve it through regexp (not ruby), you should match whole string, not substrings. Well, I added [|] symbol and line ending to your regexp and it should works like you want.
([1-9][0-9]*[=][0-9\.]+[|]*)+$
Try it out.