我需要做一个简单的字符串分割,但似乎没有一个函数,我测试的手动方式似乎不起作用。我该怎么做呢?


当前回答

我使用上面的例子来创建我自己的函数。但对我来说,缺失的部分是自动逃脱魔法角色。

以下是我的观点:

function split(text, delim)
    -- returns an array of fields based on text and delimiter (one character only)
    local result = {}
    local magic = "().%+-*?[]^$"

    if delim == nil then
        delim = "%s"
    elseif string.find(delim, magic, 1, true) then
        -- escape magic
        delim = "%"..delim
    end

    local pattern = "[^"..delim.."]+"
    for w in string.gmatch(text, pattern) do
        table.insert(result, w)
    end
    return result
end

其他回答

对于那些从“在Lua中编程”这本书的练习10.1中学习过的人来说,似乎很清楚我们不能使用后面书中解释的概念(迭代器),而且函数应该接受多个字符分隔符。

split()是一个让模式匹配不需要的内容(split)并在空字符串上返回一个空表的技巧。plainSplit()的返回更像其他语言中的split。

magic = "([%%%.%(%)%+%*%?%[%]%^%$])"

function split(str, sep, plain)
    if plain then sep = string.gsub(sep, magic, "%%%1") end
    
    local N = '\255'
    str = N..str..N
    str = string.gsub(str, sep, N..N)

    local result = {}
    for word in string.gmatch(str, N.."(.-)"..N) do
        if word ~= "" then
            table.insert(result, word)
        end
    end
    return result
end


function plainSplit(str, sep)
    sep = string.gsub(sep, magic, "%%%1")

    local result = {}
    local start = 0
    repeat
        start = start + 1

        local from, to = string.find(str, sep, start)
        from = from and from-1
        
        local word = string.sub(str, start, from, true)
        table.insert(result, word)

        start = to
    until start == nil

    return result
end


function tableToString(t)
    local ret = "{"
    for _, word in ipairs(t) do
        ret = ret .. '"' .. word .. '", '
    end
    ret = string.sub(ret, 1, -3)
    ret = ret .. "}"

    return #ret > 1 and ret or "{}"
end

function runSplit(func, title, str, sep, plain)
    print("\n" .. title)
    print("str: '"..str.."'")
    print("sep: '"..sep.."'")
    local t = func(str, sep, plain)
    print("-- t = " .. tableToString(t))
end



print("\n\n\n=== Pattern split ===")
runSplit(split, "Exercice 10.1", "a whole new world", " ")
runSplit(split, "With trailing seperator", "  a  whole   new world  ", " ")
runSplit(split, "A word seperator", "a whole new world", " whole ")
runSplit(split, "Pattern seperator", "a1whole2new3world", "%d")
runSplit(split, "Magic characters as plain seperator", "a$.%whole$.%new$.%world", "$.%", true)
runSplit(split, "Control seperator", "a\0whole\1new\2world", "%c")
runSplit(split, "ISO Time", "2020-07-10T15:00:00.000", "[T:%-%.]")

runSplit(split, " === [Fails] with \\255 ===", "a\255whole\0new\0world", "\0", true)

runSplit(split, "How does your function handle empty string?", "", " ")



print("\n\n\n=== Plain split ===")
runSplit(plainSplit, "Exercice 10.1", "a whole new world", " ")
runSplit(plainSplit, "With trailing seperator", "  a  whole   new world  ", " ")
runSplit(plainSplit, "A word seperator", "a whole new world", " whole ")
runSplit(plainSplit, "Magic characters as plain seperator", "a$.%whole$.%new$.%world", "$.%")

runSplit(plainSplit, "How does your function handle empty string?", "", " ")

输出

=== Pattern split ===

Exercice 10.1
str: 'a whole new world'
sep: ' '
-- t = {"a", "whole", "new", "world"}

With trailing seperator
str: '  a  whole   new world  '
sep: ' '
-- t = {"a", "whole", "new", "world"}

A word seperator
str: 'a whole new world'
sep: ' whole '
-- t = {"a", "new world"}

Pattern seperator
str: 'a1whole2new3world'
sep: '%d'
-- t = {"a", "whole", "new", "world"}

Magic characters as plain seperator
str: 'a$.%whole$.%new$.%world'
sep: '$.%'
-- t = {"a", "whole", "new", "world"}

Control seperator
str: 'awholenewworld'
sep: '%c'
-- t = {"a", "whole", "new", "world"}

ISO Time
str: '2020-07-10T15:00:00.000'
sep: '[T:%-%.]'
-- t = {"2020", "07", "10", "15", "00", "00", "000"}

 === [Fails] with \255 ===
str: 'a�wholenewworld'
sep: ''
-- t = {"a"}

How does your function handle empty string?
str: ''
sep: ' '
-- t = {}



=== Plain split ===

Exercice 10.1
str: 'a whole new world'
sep: ' '
-- t = {"a", "whole", "new", "world"}

With trailing seperator
str: '  a  whole   new world  '
sep: ' '
-- t = {"", "", "a", "", "whole", "", "", "new", "world", "", ""}

A word seperator
str: 'a whole new world'
sep: ' whole '
-- t = {"a", "new world"}

Magic characters as plain seperator
str: 'a$.%whole$.%new$.%world'
sep: '$.%'
-- t = {"a", "whole", "new", "world"}

How does your function handle empty string?
str: ''
sep: ' '
-- t = {""}

因为剥猫皮的方法不止一种,下面是我的方法:

代码:

#!/usr/bin/env lua

local content = [=[
Lorem ipsum dolor sit amet, consectetur adipisicing elit,
sed do eiusmod tempor incididunt ut labore et dolore magna 
aliqua. Ut enim ad minim veniam, quis nostrud exercitation 
ullamco laboris nisi ut aliquip ex ea commodo consequat.
]=]

local function split(str, sep)
   local result = {}
   local regex = ("([^%s]+)"):format(sep)
   for each in str:gmatch(regex) do
      table.insert(result, each)
   end
   return result
end

local lines = split(content, "\n")
for _,line in ipairs(lines) do
   print(line)
end

输出: 圣洁圣洁的人, sed做eiusmod时间incididunt ut并dolore麦格纳 aliqua。Ut enim ad minivenim, quis nostrud practice 这一切都是徒劳的结果。

解释:

gmatch函数作为一个迭代器,它获取所有与regex匹配的字符串。正则表达式接受所有字符,直到找到分隔符为止。

一种别人没有的方式

function str_split(str, sep)
    if sep == nil then
        sep = '%s'
    end 

    local res = {}
    local func = function(w)
        table.insert(res, w)
    end 

    string.gsub(str, '[^'..sep..']+', func)
    return res 
end

我喜欢这个简短的解决方案

function split(s, delimiter)
    result = {};
    for match in (s..delimiter):gmatch("(.-)"..delimiter) do
        table.insert(result, match);
    end
    return result;
end

我使用上面的例子来创建我自己的函数。但对我来说,缺失的部分是自动逃脱魔法角色。

以下是我的观点:

function split(text, delim)
    -- returns an array of fields based on text and delimiter (one character only)
    local result = {}
    local magic = "().%+-*?[]^$"

    if delim == nil then
        delim = "%s"
    elseif string.find(delim, magic, 1, true) then
        -- escape magic
        delim = "%"..delim
    end

    local pattern = "[^"..delim.."]+"
    for w in string.gmatch(text, pattern) do
        table.insert(result, w)
    end
    return result
end