Is underscore "_" considered as special character in US English ?
Basically i am not able to figure out if I will validate my java script text with underscore as a special character.
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I found a code with regex where it is claimed that it strips the text of any non-ASCII characters.
The code is written in Perl and the part of code that does it is:
$sentence =~ tr/\000-\011\013-\014\016-\037\041-\055\173-\377//d;
I want to understand how this regex works and in order to do this I have used regexr. I found out that \000, \011, \013, \014, \016, \037, \041, \055, \173, \377 mean separate characters as NULL, TAB, VERTICAL TAB ... But I still do not get why "-" symbols are used in the regex. Do they really mean "dash symbol" as shown in regexr or something else? Is this regex really suited for deleting non-ASCII characters?
This isn't really a regex. The dash indicates a character range, like inside a regex character class [a-z].
The expression deletes some ASCII characters, too (mainly whitespace) and spares a range of characters which are not ASCII; the full ASCII range would simply be \000-\177.
To be explicit, the d flag says to delete any characters not between the first pair of slashes. See further the documentation.
Normally, for simple character strings, a leading backtick does the trick.
Example: `abc
However, if the string has some special characters, such as space, this will not work.
Example: `$"abc def"
Example: `$"BAT-3Kn.BK"
What are the rules when $"" is required?
Simple syntax for symbols can be used when the symbol consists of alphanumeric characters, dots (.), colons (:), and (non-leading) underscores (_). In addition, slashes (/) are allowed when there is a colon before it. Everything else requires the `$"" syntax.
The book 'Q for mortals', which is available online, has a section discussing datatypes. For symbols it states:
A symbol can include arbitrary text, including text that cannot be
directly entered from the console – e.g., embedded blanks and special
characters such as back-tick. You can manufacture a symbol from any
text by casting the corresponding list of char to a symbol. (You will
need to escape special characters into the string.) See §6.1.5 for
more on casting.
q)`$"A symbol with blanks and `"
`A symbol with blanks and `
The essential takeaway here is that converting a string to a symbol is required when special characters are involved. In the examples you have given both space " " and hyphen "-" are characters that cannot be directly placed into a symbol type.
I've read that we must use Unicode values inside the content CSS property i.e. \ followed by the special character's hexadecimal number.
But what characters, other than alphanumerics, are actually allowed to be placed as is in the value of content property? (Google has no clue, hence the question.)
The rules for “escaping” characters are in the CSS 2.1 specification, clause 4.1.3 Characters and case. The special rules for quoted strings, as in content property value, are in clause 4.3.7 Strings. Within a quoted string, any character may appear as such, except for the character used to quote the string (" or '), a newline character, or a backslash character \.
The information that you must use \ escapes is thus wrong. You may use them, and may even need to use them if the character encoding of the document containing the style sheet does not let you enter all characters directly. But if the encoding is UTF-8, and is properly declared, then you can write content: '☺ Я Ω ⁴ ®'.
As far as I know, you can insert any Unicode character. (Here's a useful list of Unicode characters and their codes.)
To utilize these codes, you must escape them, like so:
U+27BA Becomes \27BA
Or, alternatively, I think you may just be able to escape the character itself:
content: '\➺';
Source: http://mathiasbynens.be/notes/css-escapes
I am using multilingual characters, use utf8 encoding. Now i need to validate it and avoid special characters while entering it.Is there any way to identify special characters while using multilingual character inputs? what i mean is we can validate special chars like !#%%^&.. while using english.I am looking for the same type of validation.
anybody please help me...
I am using zend php.
thanks in advance.
There's only one "!", "#", "%", "^" and "&" character respectively. There's not an "English !" and a "Spanish !" and an "Indian !" and a "Korean !". They're all the same character. If they're encoded in UTF-8, they're even the same byte as ASCII encoded characters. You can look for them and replace them as before.
There may be characters that look similar, like "！" (fullwidth exclamation mark), but that's not the same character as "!" and hence does not have a special meaning if "!" has a special meaning.
Use the Zend_Validate_Alnum validator, it's unicode ready.
how can i extract only the characters in a particular language from a file containing language characters, alphanumeric character english alphabets
This depends on a few factors:
Is the string encoded with UTF-8?
Do you want all non-English characters, including things like symbols and punctuation marks, or only non-symbol characters from written languages?
Do you want to capture characters that are non-English or non-Latin? What I mean is, would you want characters like é and ç or would you only want characters outside of Romantic and Germanic alphabets?
and finally,
What programming language are you wanting to do this in?
Assuming that you are using UTF-8, you don't want basic punctuation but are okay with other symbols, and that you don't want any standard Latin characters but would be okay with accented characters and the like, you could use a string regular expression function in whatever language you are using that searches for all non-Ascii characters. This would elimnate most of what you probably are trying to weed out.
In php it would be:
$string2 = preg_replace('/[^(\x00-\x7F)]*/','', $string1);
However, this would remove line endings, which you may or may not want.