# Parsing literals

**URL:** <https://www.ruby-forum.com/t/parsing-literals/101236>\
**Category:** Ruby\
**Created:** [December 14, 2005, 3:29am UTC](https://www.ruby-forum.com/t/parsing-literals/101236 "2005-12-14T03:29:06Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![akoSS](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/47e85d/32.png) [@akoSS](https://www.ruby-forum.com/u/akoSS)\
**Post date:** [December 14, 2005, 3:29am UTC](https://www.ruby-forum.com/t/parsing-literals/101236/1 "2005-12-14T03:29:06Z")

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hello,

i need to write a function that would parse a string literal in another  
language. a string literal in this language is:

STRING = “CHAR\*”  
CHAR = any character except for " and   
| "  
| \  
| /  
| \u four hexadecimal digits

the \u sequence specifies a character in UTF-16 encoding.

for example: “abc”, “”, “a"bc”, “a\b”, “a\u12bfc”

below is the code that i wrote. is this Ruby enough? can someone  
suggest improvements? a better style?

thanks  
konstantin

def parselit(s)  
r = %r{\"|\/|\\|\u[\da-f][\da-f][\da-f][\da-f]}i  
s =~ /^"((?:[^"\]|#{r})_)"$/ && $1.gsub® { |x| x =~ /\u(._)/ ?  
[$1.hex].pack(‘U\*’) : x[1…-1] }  
end

puts parselit(’"\u004e"a"’)

---

<div class="post-metadata">

**Author:** ![akoSS](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/47e85d/32.png) [@akoSS](https://www.ruby-forum.com/u/akoSS)\
**Post date:** [December 14, 2005, 12:14pm UTC](https://www.ruby-forum.com/t/parsing-literals/101236/2 "2005-12-14T12:14:31Z")

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ako… wrote:

> | \u four hexadecimal digits
> 
> def parselit(s)  
> r = %r{\"|\/|\\|\u[\da-f][\da-f][\da-f][\da-f]}i  
> s =~ /^"((?:[^"\]|#{r})_)"$/ && $1.gsub® { |x| x =~ /\u(._)/ ?  
> [$1.hex].pack(‘U\*’) : x[1…-1] }  
> end
> 
> puts parselit(’"\u004e"a"’)

def parselit(s)

re = %r{  
\"  
| \/  
| \\  
| \u [\da-f] {4}  
}xoi

return nil if s !~ /^".\*"$/

out = “”

s[1…-2].scan( /\G (?: ( [^"\]+ ) | ( #{re} ) )/x ){ |x|  
out \<\<  
if !x.last  
x.first  
else  
if x.last[0,2] == ‘\u’  
[x.last[2…-1].hex].pack(‘U\*’)  
else  
x.last[1…-1]  
end  
end

}

# Fail if whole string didn’t match.

if $~.post\_match != “”  
nil  
else  
out  
end

end

puts parselit(’"\u004e"a"’)  
puts parselit(’"\u004e"“a”’)