Question

Matlab允许您在没有警告的情况下覆盖内置函数。

例如，我用变量覆盖了函数max()，但Matlab并没有提醒我这一点。只有在调用函数时才会抛出错误，并且无法帮助您查看实际问题：

min     = 0;
max     = 10;
x       = linspace(min,max,20);
y       = exp(x);
disp(['the value is: ', num2str(max(y))])

错误讯息：

Subscript indices must either be real positive integers or logicals.

有没有办法在启动时或在设置文件中写保护所有Matlab语言以防止这种情况？

Answer 1

我不知道如何做你想做的事。但是有一种方法可以使用which通过变量或其他函数检查特定函数是否被阴影：即分析which(fname, '-all')的输出，其中fname是一个包含函数名称的字符串。

以max函数为例：比较（无阴影）

>> clear all
>> fname = 'max';
>> which(fname, '-all')
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@logical\max)  % logical method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@char\max)     % char method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@double\max)   % double method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint8\max)    % uint8 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint16\max)   % uint16 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint32\max)   % uint32 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint64\max)   % uint64 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int8\max)     % int8 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int16\max)    % int16 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int32\max)    % int32 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int64\max)    % int64 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@single\max)   % single method
C:\Program Files\MATLAB\R2010b\toolbox\matlab\timeseries\@timeseries\max.m     % timeseries method
C:\Program Files\MATLAB\R2010b\toolbox\distcomp\parallel\@codistributed\max.m  % codistributed method
C:\Program Files\MATLAB\R2010b\toolbox\shared\statslib\@ordinal\max.m          % ordinal method

with（shadowing）

>> fname = 'max';
>> max = 10;
>> which(fname, '-all')
max is a variable.
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@logical\max)  % Shadowed logical method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@char\max)     % Shadowed char method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@double\max)   % Shadowed double method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint8\max)    % Shadowed uint8 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint16\max)   % Shadowed uint16 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint32\max)   % Shadowed uint32 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint64\max)   % Shadowed uint64 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int8\max)     % Shadowed int8 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int16\max)    % Shadowed int16 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int32\max)    % Shadowed int32 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int64\max)    % Shadowed int64 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@single\max)   % Shadowed single method
C:\Program Files\MATLAB\R2010b\toolbox\matlab\timeseries\@timeseries\max.m     % Shadowed timeseries method
C:\Program Files\MATLAB\R2010b\toolbox\distcomp\parallel\@codistributed\max.m  % Shadowed codistributed method
C:\Program Files\MATLAB\R2010b\toolbox\shared\statslib\@ordinal\max.m          % Shadowed ordinal method

在第二种情况下，which(fname, '-all')告诉您max是一个隐藏多种方法的变量。

因此，要测试阴影是否正在发生，

将which(fname, '-all')的输出分配给变量。

原则上，这可以s = which(fname, '-all');完成。然而不幸的是，这会产生不同的输出;特别是，上面行中的% ...部分（告知是否有阴影）被删除：

>> fname = 'max';
>> s = which(fname, '-all')
s = 
    'variable'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@logical\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@char\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@double\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint8\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint16\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint32\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint64\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int8\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int16\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int32\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int64\max)'
    'built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@single\max)'
    'C:\Program Files\MATLAB\R2010b\toolbox\matlab\timeseries\@timeseries\max.m'
    'C:\Program Files\MATLAB\R2010b\toolbox\distcomp\parallel\@codistributed\max.m'
    'C:\Program Files\MATLAB\R2010b\toolbox\shared\statslib\@ordinal\max.m'

因此，我们需要求助于evalc以获得完整的输出：s = evalc('which(fname, ''-all'')');。结果s是一个长字符串，其中包含换行符分隔的所有行（包括% ...部分）：

>> fname = 'max';
>> s = evalc('which(fname, ''-all'')')
s =
max is a variable.
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@logical\max)  % Shadowed logical method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@char\max)     % Shadowed char method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@double\max)   % Shadowed double method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint8\max)    % Shadowed uint8 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint16\max)   % Shadowed uint16 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint32\max)   % Shadowed uint32 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@uint64\max)   % Shadowed uint64 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int8\max)     % Shadowed int8 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int16\max)    % Shadowed int16 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int32\max)    % Shadowed int32 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@int64\max)    % Shadowed int64 method
built-in (C:\Program Files\MATLAB\R2010b\toolbox\matlab\datafun\@single\max)   % Shadowed single method
C:\Program Files\MATLAB\R2010b\toolbox\matlab\timeseries\@timeseries\max.m     % Shadowed timeseries method
C:\Program Files\MATLAB\R2010b\toolbox\distcomp\parallel\@codistributed\max.m  % Shadowed codistributed method
C:\Program Files\MATLAB\R2010b\toolbox\shared\statslib\@ordinal\max.m          % Shadowed ordinal method

分析在步骤1中获取的字符串s，看它是否包含'% Shadowed'。这可以通过strfind轻松完成：即如果有阴影，strfind(s, '% Shadowed')将为非空。

总结：

全部放在一起，

isShadowed = ~isempty(strfind(evalc('which(fname, ''-all'')'), '% Shadowed'));

true

返回fname，否则返回false。

变量示例：

>> clear all
>> fname = 'max';
>> max = 10;
>> isShadowed = ~isempty(strfind(evalc('which(fname, ''-all'')'), '% Shadowed'))
isShadowed =
     1
>> clear max
>> isShadowed = ~isempty(strfind(evalc('which(fname, ''-all'')'), '% Shadowed'))
isShadowed =
     0

具有指定功能的示例：

在文件std.m中创建一个函数并将其放在路径中。这将影响Matlab的std函数。

>> fname = 'std';
>> isShadowed = ~isempty(strfind(evalc('which(fname, ''-all'')'), '% Shadowed'))
isShadowed =
     1

现在删除功能文件（或从路径中删除其文件夹）：

>> fname = 'std';
>> isShadowed = ~isempty(strfind(evalc('which(fname, ''-all'')'), '% Shadowed'))
isShadowed =
     0

匿名函数示例：

>> std = @(x) x+1;
>> fname = 'std';
>> isShadowed = ~isempty(strfind(evalc('which(fname, ''-all'')'), '% Shadowed'))
isShadowed =
     1
>> clear std
>> isShadowed = ~isempty(strfind(evalc('which(fname, ''-all'')'), '% Shadowed'))
isShadowed =
     0

Answer 2

截至2015年9月，我还没有找到一种方法轻松写保护原生matlab函数/语言，作为启动时的设置/标志/等。

如果您担心特定功能，可以通过多种方式查看它们是否被隐藏，包括Luis Mendo的回答：which('name_of_function', '-all')。

如果将来找到某种方法，我很乐意接受这个答案！

如何写保护Matlab语言？

2 个答案: