Especially for Perl programmers, Lua's lack of text processing power can be an annoyance. Here are some mostly Perl-inspired routines to take away some of the pain:

[!] VersionNotice: The below code pertains to an older Lua version, Lua 4. It does not run as is under Lua 5.

-- Write a line adding \n to the end
-- [fp]: file handle
-- s: string to write
function writeLine(fp, s)
 if not s then s, fp = fp, nil end
 if fp then write(fp, s .. "\n")
 else write(s .. "\n")
 end
end
-- Remove any final \n from a string.
-- s: string to process
-- returns
-- s: processed string
function chomp(s)
 return gsub(s, "\n$", "")
end
-- Escape a string to be used as a pattern
-- s: string to process
-- returns
-- s: processed string
function escapePattern(s)
 s = gsub(s, "(%W)", "%%%1")
 return s
end
-- Escape a string to be used as a shell token (quote spaces and \s)
-- s: string to process
-- returns
-- s: processed string
function escapeShell(s)
 s = gsub(s, "([ %(%)])", "\\%1")
 return s
end
-- Turn a list of strings into a sep-separated string
-- sep: separator
-- l: list of strings to join
-- returns
-- s: joined up string
function join(sep, l)
 local len = getn(l)
 if len == 0 then return "" end
 local s = l[1]
 for i = 2, len do s = s .. sep .. l[i] end
 return s
end
-- Justify a string
-- s: string to justify
-- width: width to justify to (+ve means right-justify; negative
-- means left-justify)
-- [padder]: string to pad with (" " if omitted)
-- returns
-- s: justified string
function pad(s, width, padder)
 padder = strrep(padder or " ", abs(width))
 if width < 0 then return strsub(padder .. s, width) end
 return strsub(s .. padder, 1, width)
end
-- Wrap a string into a paragraph
-- s: string to wrap
-- w: width to wrap to [78]
-- i1: indent of first line [0]
-- i2: indent of subsequent lines [0]
-- returns
-- s: wrapped paragraph
function wrap(s, w, i1, i2)
 w = w or 78
 i1 = i1 or 0
 i2 = i2 or 0
 affirm(i1 < w and i2 < w,
 "wrap: the indents must be less than the line width")
 s = strrep(" ", i1) .. s
 local lstart, len = 1, strlen(s)
 while len - lstart > w do
 local i = lstart + w
 while i > lstart and strsub(s, i, i) ~= " " do i = i - 1 end
 local j = i
 while j > lstart and strsub(s, j, j) == " " do j = j - 1 end
 s = strsub(s, 1, j) .. "\n" .. strrep(" ", i2) ..
 strsub(s, i + 1, -1)
 local change = i2 + 1 - (i - j)
 lstart = j + change
 len = len + change
 end
 return s
end
-- readLines: read _INPUT into a list of lines
-- returns
-- line: list of lines
function readLines()
 local line = {}
 repeat
 local l = read("*l")
 if not l then break end
 tinsert(line, l)
 until nil
 return line
end

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Last edited October 30, 2010 1:18 pm GMT (diff)