I notice some people use %(string here) instead of a simple use of double quotes as "string here". Is there any reason for this? When I use the first layout, I usually make an array such as %w(my array here) so I don't have to use quotes and commas.
Is there a hidden rule I am unaware of? I can't imagine why I would do this:
a = %(some string here)
instead of
b = "some string here"
The latter just seems more clearly written.
They are almost equivalent, using %() you don't have to escape the " character inside the string:
s = %(foo "bar" baz)
# => "foo \"bar\" baz"
They are mostly useful when your string is full of double quotes.
If you're going to have double-quotes embedded within the the string itself, it can be easier to do the %() than to properly escape all of the double-quotes. It may be more readable, too.
Related
I'm trying to use the regex /^[a-zA-Z0-9_$&+:;=?##|'<>.^*()%!-]+$/ with dart regex. I've seen you can use raw strings. So Ive put the above in between r'' like this:
r'^[a-zA-Z0-9_$&+:;=?##|'<>.^*()%!-]+$' but the ' is messing it up. How do I tell dart this is a special character..
EDIT
I tried this but it doesn't seem to work
static final RegExp _usernameRegExp = RegExp(
r"^[a-zA-Z0-9_$&+:;=?##|'<>.^*()%!-]+$",
);
So I have a TextField with a text controller for a username. A method like this
static bool isValidUsername(String username) {
return (_usernameRegExp.hasMatch(username));
}
I pass the controller.text as the username.
I've a function:
bool get isUserNameValid => (Validators.isValidUsername(userNameTextController.text.trim()));
I can type all the given characters in to the textbook but not '
Your RegExp source contains ', so you can't use that as string delimiter without allowing escapes. It also contains $ so you want to avoid allowing escapes.
You can use " as delimiter instead, so a raw string like r"...".
However, Dart also has "multi-line strings" which are delimited by """ or '''. They can, but do not have to, contain newlines. You can use those for strings containing both ' and ". That allows r'''...'''.
And you can obviously also use escapes for all characters that mean something in a string literal.
So, for your code, that would be one of:
r'''^[\w&+:;=?##|'<>.^*()%!-]+$'''
r"^[\w&+:;=?##|'<>.^*()%!-]+$"
'^[\\w&+:;=?##|\'<>.^*()%!-]+\$'
(I changed A-Za-z0-9$_ to \w, because that's precisely what \w means).
In practice, I'll always use a raw string for regexps. It's far too easy, and far too dangerous, to forget to escape a backslash, so use one of the first two options.
I'd probably escape the - too, making it [....\-] instead of relying on the position to make it non-significant in the character class. It's a fragile design that breaks if yo add one more character at the end of the character class, instead of adding it before the -. It's less fragile if you escape the -.
I am working on string manipulation using LUA and having trouble with the following problem.
Using this as an example of the original data I am given -
"[0;1;36m(Web): You say, "Text here."[0;37m"
I want to keep the string intact except for removing the ANSI codes.
I have been pointed toward using gsub with the LUA pattern matching but I cannot seem to get the pattern correct. I am also unsure how to reference exactly the escape character sent.
text:gsub("[\27\[([\d\;]+)m]", "")
or
text:gsub("%x%[[%d+;+]m", "")
If successful, all I want to be left with, using the above example, would be:
(Web): You say, "Text here."
Your string example is missing the escape character, ASCII 27.
Here's one way:
s = '\x1b[0;1;36m(Web): You say, "Text here."\x1b[0;37m'
s = s:gsub('\x1b%[%d+;%d+;%d+;%d+;%d+m','')
:gsub('\x1b%[%d+;%d+;%d+;%d+m','')
:gsub('\x1b%[%d+;%d+;%d+m','')
:gsub('\x1b%[%d+;%d+m','')
:gsub('\x1b%[%d+m','')
print(s)
I am trying to set an email address within ActionMailer with Rails. Before it was hard coded, but we want to make them ENV variables now so we don't need to amend code each time an email changes.
Here is how it's currently defined:
from = '"Name of Person" <email#email.com>'
I've tried setting the email as an environment variable using ENV['EMAIL'] but I'm having no luck even with #{ENV['EMAIL'}.
Can anyone point me in the right direction?
You cannot use string interpolation with single-quoted strings in Ruby.
But double-quoted strings can!
from = "'Name of Person' <#{ENV['EMAIL']}>"
But if you want to keep your double-quotes wrapping the Name of Person, you can escape them with a backslash \:
from = "\"Name of Person\" <#{ENV['EMAIL']}>"
Or use string concatenation:
from = '"Name of Person" <' + ENV['EMAIL'] + '>'
# but I find it ugly
If you want to embed double quotes in an interpolated string you can use % notation delimiters (which Ruby stole from Perl), e.g.
from = %|"Name of Person", <#{ENV['EMAIL']}>|
or
from = %("Name of Person", <#{ENV['EMAIL']}>)
Just pick a delimiter after the % that isn't already in your string.
You can also use format. I have not seen it used as commonly in Ruby as in other languages (e.g. C, Python), but it works just as well:
from = format('"Name of Person", <%s>', ENV["EMAIL"])
Alternative syntax using the % operator:
from = '"Name of Person", <%s>' % ENV["EMAIL"]
Here is the documentation for format (aka sprintf):
http://ruby-doc.org/core-2.2.0/Kernel.html#method-i-format
I have two strings - each string has many lines like the following:
string1 = " DEFAULT-VLAN | Manual 10.1.1.3 255.255.255.0 "
string2 = " 1 DEFAULT-VLAN | Port-based No No"
The first string I split into the following strings: "DEFAULT-VLAN", "|", "Manual"...
Then I want to look up the ID ("1") in string2 for the vlanName ("DEFAULT-VLAN") from string1.
I use this code to find the correct substring:
vpos1, vpos2 = vlan:find("%d-%s-" .. vlanName .. "%s-|")
But vpos1 and vpos2 are nil; When the hyphen ("-") is deleted from the vlanName it is working.
Shouldn't Lua take care to escape the special characters in such strings? The string is handed over from my C++ application to Lua and there may be lots of special characters.
Is there an easy way to solve this?
Thanks!
Lua is not magic. All the expression "%d-%s-" .. vlanName .. "%s-|" does is concatenate some strings, producing a final string. It has no idea what that string is intended to be used for. Only string.find knows that, and it can't have any affect on how the parameter it is given will be used.
So yes, vlanName will be interpreted as a Lua pattern. And if you want to use special characters, you will need to escape them. I would suggest using string.gsub for that. It'd be something like this:
vlanName:gsub("[%-...]", "%%%0")
Where ... are any other characters you want to escape.
How do I remove this backslash?
s = "\""
I have tried s.gsub("\\", "") and that doesn't remove it, it returns the same string.
there's actually no backslash character in your String. The Backslash in your example simply escapes the following double quote and prevent's that it would terminate the string and thereby resulting in a syntax error (unterminated double quote ).
So what you see when you print that string in IRB is actually not the backslash as is, but the backslash in combination with the following dobule quote as an indication that the double quote is escaped. Kind of hard to grasp when you encounter it the first time. Have a look at http://en.wikibooks.org/wiki/Ruby_Programming/Strings#Escape_sequences
long story short: there is no backslash in your string so you can't remove it :)
gsub takes a regular expression as the first parameter. I believe that if you pass it a string, it will first convert it into a regex. This means you need extra escaping:
s.gsub("\\\\", "")
If you use regex notation, you can stop it from doubling up:
s.gsub(/\\/, "")
This is because you don't have to escape twice: once because double-quoted strings need you to escape the \ character, and once because the regular expression requires you to as well.
that's actually an escape quote sign (do a print s to see it)
I'm not sure if this is a solution to YOUR problem, but seeing that this is one of the first SO questions I looked at when trying to solve my problem and have in fact, solved it, here is what I did to fix my problem.
So I had some CSV.read output with a load of \ (backslashes) and unwanted quotation marks.
arr_of_arrays = CSV.read("path/to/file.csv")
processed_csv = arr_of_arrs.map {|t| eval(t)}
the key here is the eval() method.