Re: quoting unquoted token?
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- Subject: Re: quoting unquoted token?
- From: Peter Odding <peter@...>
- Date: 2011年10月05日 22:25:34 +0200
Hello,
What would be a reasonable way to, hmmm, quote unquoted tokens?
Say a token is an uninterrupted sequence of alphanumeric characters
(%w) or a quoted token. A quoted token is any sequence of characters
inside quotes, minus any quote characters.
For example:
'foo "hello world" bar'
How to turn the above into:
'"foo" "hello world" "bar"'
Thoughts?
You can do this in plain Lua but it's not nice, I would prefer LPeg:
----
lpeg = require 'lpeg'
whitespace = lpeg.S'\r\n\f\t '^1
unquoted = lpeg.R('AZ', 'az', '09')^1
single_quoted = "'" * (1 - lpeg.P"'")^0 * "'"
double_quoted = '"' * (1 - lpeg.P'"')^0 * '"'
any = lpeg.C(whitespace + unquoted + single_quoted + double_quoted)
function quote_tokens(input)
local i = 1
local output = {}
while true do
local match = any:match(input, i)
if not match then
break
else
i = i + #match
if match:find '%S+' then
if match:find '^[A-Za-z0-9]+$' then
match = '"' .. match .. '"'
end
output[#output + 1] = match
end
end
end
return table.concat(output, ' ')
end
assert(quote_tokens 'foo bar baz' == '"foo" "bar" "baz"')
assert(quote_tokens 'foo "bar" baz' == '"foo" "bar" "baz"')
assert(quote_tokens "foo 'bar' baz" == '"foo" \'bar\' "baz"')
----
One notable advantage of LPeg is that it's dead easy to extend this
example with support for escape sequences and stuff like that :-)
- Peter