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I'd like to try Ruby for something I did in Python. In Python it has the r""" syntax to support raw strings, which is nice as it allows one to have raw strings in-line with the code and to concatenate them in more natural way and with no special indentation needed. In Ruby, when using raw strings, one has to use <<'EOT' followed by EOT in separate line which breaks the code layout.
You might ask, why not then use Ruby's %q{}? Well, because %q{} has limitations compared to Python's r""" as it does not escape multiple \\\ and only handles single \.
I am generating Latex code on the fly and write to a file, which later is compiled with pdflatex. The Latex code contain things like \\\ in many places. If I use Ruby's %q{} syntax, then it will not work. So I have to use Ruby's <<'EOT' but I do not want to do this, as it makes the code harder to read in the Ruby source file due to having to break it for indentation to make EOT happy.
I am asking if there is a way to make syntax similar to %q{}, or some function that take string and return same result as if one used EOT, that handles raw strings without the limitation of EOT.
I do not need interpolation. So single quoted strings only. No double quoted. double quotes causes interpolation, which I do not want.
Here is a small example in Python, and then I show what I have to do in Ruby to generate the same output.
my_file = open("py_latex.tex", 'w')
x = r"""\\\hline is a raw string"""+r""" another one \\\hline and so on"""
my_file.write(x)
When I open the Latex text file written to in the above, I see the correct result
Now to do the same thing in Ruby. I can't write the following (even though I'd like to)
file = File.open('rb_latex.tex','w')
x=%q{\\\hline is a raw string}+%q{ another one \\\hline and so on}
file.write(x)
The above ofcourse is not what I want. When it is written to latex file, it shows up as
Using EOT works, as follows
file = File.open('rb_latex.tex','w')
x=<<-'EOT1'+<<-'EOT2'
\\\hline is a raw string
EOT1
another one \\\hline and so on
EOT2
file.write(x)
And the file now is
ps. it makes the second string on new line, this is a side-issue for me now, and will try to find solution for this after I solve the main problem at hand.
How to make %q{} like syntax for Ruby that works similar to Python r""" ?
If someone wants to try the above code in Ruby, make sure there is no space after EOT. I also include below the full source code.
Python full source
import os
os.chdir(" direct to change to here ")
my_file = open("py_latex.tex", 'w')
x = r"""\\\hline is a raw string"""+r""" another one \\\hline and so on"""
my_file.write(x)
my_file.close()
Ruby source code
#!/usr/local/bin/ruby -w
Dir.chdir("/home/....")
file = File.open('rb_latex.tex','w')
#x=%q{\\\hline is a raw string}+%q{ another one \\\hline and so on}
x=<<-'EOT1'+<<-'EOT2'
\\\hline is a raw string
EOT1
another one \\\hline and so on
EOT2
file.write(x)
file.close
Update
To answer comment below:
The idea is that it is supposed to act exactly like HERE-DOCUMENT, but with the nice syntax of %q{} to allow one to more easier format the string in the ruby source code. i.e. anything inside should be written to the file as is, no matter what it is.
I tested the solution provided below, but it does not work for all cases. Here is a test case:
#!/usr/local/bin/ruby -w
class String
def raw
gsub('\\'*2) { '\\'*3 }
end
end
class Array
def raw(separator = $,)
map(&:raw).join(separator)
end
end
Dir.chdir("/home/me")
file = File.open('rb_latex.tex','w')
x=%q{'\\'\hline \\\\\\ (6 of them) // some stuff follows. All should be raw string
<!DOCTYPE html>
\[ stuff \]
<html>
<head>
<title>title</title>
<style>
video {
width: 100% !important;
eight: auto !important;
}
</html> \"quotes\" (did you see this?)
\\\hline $\sin(x)$
</style>' //notice this ' is in the raw string!, ok!
\begin{tabular}{c}\\\hline '''''' (6 of them)
x\\\hline
\end{tabular}}.raw+%q{another '''one \\\hline and so on'}.raw
file.write(x)
file.close
Looking at the file written, it is not the same as the raw string:
Now compare with Python r"""
import os
os.chdir("/home/me")
my_file = open("py_latex.tex", 'w')
x =r"""\\'\hline \\\\\\ (6 of them) // some stuff follows. All should be raw string
<!DOCTYPE html>
\[ stuff \]
<html>
<head>
<title>title</title>
<style>
video {
width: 100% !important;
eight: auto !important;
}
</html> \"quotes\" (did you see this?)
\\\hline $\sin(x)$
</style>' //notice this ' is in the raw string!, ok!
\begin{tabular}{c}\\\hline '''''' (6 of them)
x\\\hline
\end{tabular}}"""+r"""{another '''one \\\hline and so on'"""
my_file.write(x)
my_file.close()
Here is the output
And the above is what I want to obtain from Ruby as well.
937
Use the + Operator for Writing Multi-Line String in Ruby The string concatenation operator is naive to write multi-line strings in Ruby. Unlike the above method, using + does not preserve whitespaces or newlines.
We can use string literal concatenation. Multiple string literals in a row are joined together: char* my_str = "Here is the first line." "Here is the second line."; But wait!
Strings are most often created with a String literal. A literal is a special syntax in the Ruby language that creates an object of a specific type. For example, 23 is a literal that creates a Fixnum object. As for String literals, there are several forms.
Alternate double quotes The %Q operator (notice the case of Q in %Q ) allows you to create a string literal using double-quoting rules, but without using the double quote as a delimiter. It works much the same as the %q operator.
To deal with indentation issues in here documents, one approach is to monkey-patch the core String class, adding an instance method String#undent:
class String
def undent
indentation = slice(/^\s+/).length
gsub(/^.{#{ indentation }}/, '')
end
end
Then you could rewrite your code like this:
x = <<-'EOT'.undent
\\\hline is a raw string
another one \\\hline and so on
EOT
Note: Patching core classes is generally considered bad style and might compromise stability and maintainability. That said, I feel that patching String to add #undent is a sensible exception. That method just has so many benefits and it is not really that invasive.
Ultimately, it’s up to you to weigh the pros and cons.
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