Erlang实战文本排版

文本排版大家都并不陌生,并且随处可见,无论是当前的字处理软件,如Word、PDF等,还是传统的出版行业,如:书籍、报刊、杂志等,都有良好的排版风格和样式。好的排版风格让人耳目一新,有一种继续读下去的**。本文主要是通过Erlang实现简单的文本排版,借此学习Erlang、熟悉Erlang。实战:文本排版。要求如下:**://images.51cto.com/files/uploadimg/20120508/1343260.png**://images.51cto.com/files/uploadimg/20120508/1343261.png在代码中我附了注释,代码如下:
-module(text_process).
-export().
-import(lists,).

process(FileIn,FileOut) ->
{Status,Value} = file:open(FileIn,read),
if
Status =:= ok ->
Tokens = readFile(Value), %% 将要处理文本FileIn拆分为单词列表
io:format("token :~p~n",),
writeToFile(FileOut,Tokens), %% 将单词重新排版输出到屏幕与文件FileOut
io:format("~nsuccess!~n");
Status =/= ok ->
io:format("Open file error: file doesn't exist!")
end.

readFile(Value) -> readFile(Value,[]).

readFile(S,Dict) ->
OneLine = io:get_line(S,''), %%读取文件的一行
if
OneLine =:= eof ->
io:format("~nCome across the file end, stop!~n"),
file:close(S),
Dict;
OneLine =/= eof ->
Tokens = string:tokens(OneLine,"\r\t\n "), %%以空格、回车、换行、制表符为单词分隔符
Len = string:len(Tokens), %%获得字符串的长度
if
Len =:= 0 -> %%遇到空行,停止处理
io:format("~nCome across blank line, stop!~n"),
file:close(S),
Dict;
Len =/= 0 ->
NewDict = string:concat(Dict,Tokens), %% 将Tokens连接到Dict尾
readFile(S,NewDict) %%未读到空行、EOF,继续读取文本
end
end.

writeToFile(FileOut,Tokens) ->
{ok,S} = file:open(FileOut,write),
Data = parse(Tokens,[]),
String = lineToPara(Data),
io:format("~n~s~n",), %% 输出到屏幕
io:format(S,"~s~n",). %% 输出到文件
%lists:foreach(fun({X}) -> io:format(S,"~s~n",) end, Data).

lineToPara(Data) -> lineToPara(Data,"").

lineToPara([],Ret) -> Ret;
lineToPara(Data,Ret) ->
Last = lists:nth(1,Data),
Element = element(1,Last),
Temp = Ret ++ Element ++ "\n",
%io:format("~s",),
lineToPara(lists:delete(Last,Data), Temp).

%%解析单词列表
parse(Tokens,Contents) ->
M =50,
{ALine,RemainToken} = parse_line(Tokens,M),
if
length(RemainToken) =:= 0 ->
Plain = plain(ALine),
io:format("last line----:~s~n",),
NewContent = lists:append(Contents,);
length(RemainToken) =/= 0 ->
NewContent = lists:append(Contents,),
parse(RemainToken,NewContent)
end.

plain(Last) ->plain(Last, "").

plain([], String) -> String;
plain(L, String) ->
if
length(L) =:= 1 ->
Last = lists:nth(1,L),
NewS = string:concat(String,Last);
length(L) =/= 1 ->
First = lists:nth(1,L),
Temp = string:concat(First," "),
NewS = string:concat(String,Temp),
plain(lists:delete(First,L), NewS)
end.

parse_line(Tokens,M) -> parse_line(Tokens,M,[]).

%% @ Tokens: 当前剩余单词个数
%% @ M:每行最大字符阀值
%% @ Line: 当前单词行列表
parse_line([],_M,Line) -> {Line,[]};
parse_line(Tokens,M,Line) ->
if
length(Line) =:= 0 ->
Element = lists:nth(1,Tokens),
NewL = length(Element),
NewToken = lists:delete(Element,Tokens),
parse_line(NewToken,M,);
length(Line) =/= 0 ->
Element = lists:nth(1,Tokens),
NewL = len(Line)+length(Element)+length(Line),
case NewL > M of
true ->
String = toString(Line,M),
{String,Tokens};
false ->
NewLine = lists:append(Line,),
NewToken = lists:delete(Element,Tokens),
parse_line(NewToken,M,NewLine)
end
end.

%% 排版输出当前行Line数据
toString(Line,M) ->
Len = len(Line),
Blank = M - Len,
%io:format("Blank:~p Len:~p length(Line):~p ~n",),
Ret = justify(Line,Blank,length(Line)),
io:format("Mess------Ret:~s length:~p~n",),
Ret.

justify(Line,Blank,Len) -> justify(Line,Blank,Len,"").

%% @Line: 一行字符串数据
%% @Blank:需要的空格个数
%% @Len: 当前行中剩余的单词个数
%% @String: 返回一行矫正结果
justify(Line,Blank,Len,String) ->
if
length(String) =:= 0 -> %%初始情况
Temp = lists:nth(1,Line),
Avg = Blank div Len, %% 计算单词之间平均需要Avg个空格字符
NewLine = lists:delete(Temp,Line),
%io:format("1---avg: ~p Blank:~p Len: ~p~n",),
case Avg =:= 0 of
true ->
NewS = while(1,Temp),
justify(NewLine,Blank-1,length(NewLine),NewS);
false ->
NewS = while(Avg,Temp),
justify(NewLine,Blank-Avg,length(NewLine),NewS)
end;
length(String) =/= 0 ->
if
length(Line) =:= 1 -> %%一行中最后一个单词,返回结果
Last = lists:nth(1,Line),
NewS = while(Blank,String), %%将剩余的Blank个字符补全
string:concat(NewS,Last);
length(Line) =/= 1 ->
First = lists:nth(1,Line),
Avg = Blank div Len,
NewLine = lists:delete(First,Line),
%io:format("2---avg: ~p Blank:~p Len: ~p~n",),
case Avg =:= 0 of
true ->
NewS = while(1,String),
justify(NewLine,Blank-1,length(NewLine), string:concat(NewS,First));
false ->
NewS = while(Avg,String),
justify(NewLine,Blank-Avg,length(NewLine), string:concat(NewS,First))
end
end
end.

%% 功能: 子字符串后面加Count个空格
while(0,String) -> String;
while(Count,String) ->
NewS = string:concat(String," "),
while(Count-1,NewS).

%%统计一行中字符的个数(只包括单词字符,不包括空格)
len(Line) -> len(Line,0).

len([],Len) -> Len;
len(,Len) ->
len(T,Len+length(H)). 看起来比较复杂,其实思路比较简单:1.将文本切分单词列表;2.设定一个阀值M,将每行的字符设置为M,同时必须保证单词不能分割;我觉得此程序的难度主要是设定单词与单词之间的空格字符的问题,我的思路是:根据每行中所有单词所占的字符个数不同,求出单词之间空格的平均Avg个数,一般情况,单词与单词之间的字符个数为1,因此justify/4很好的处理了这个问题。程序运行结果示意图如下:**.txt文件内容:**://images.51cto.com/files/uploadimg/20120508/1343264.png结果如下:**://images.51cto.com/files/uploadimg/20120508/1343265.png好了,文档排版Erlang实战就到此为止了。说个小问题,我在Erlang实战:杨辉三角、选择排序、集合交与并中的实战2:选择排序中不是用了两次列表逆置来讲一个元素加入到列表尾吗,其实Erlang中模块lists:append可以解决这个问题,我在本文代码中多次用到了这个函数,如:NewLine = lists:append(Line,),意思就是讲Element元素加入到列表尾,但是append函数的两个参数必须都为列表,因此Element元素需以列表形式加入:,可见世上存在这样一条真理:只有你不知道的,没有不可能发生的。原文:**://**.cnblogs.com/itfreer/archive/2012/05/08/Erlang_in_practise_text-process.html
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