Using regexp to match multiple substrings, two questions

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Aram Schiffman
Aram Schiffman 2017-11-27
评论： Aram Schiffman 2017-11-27
Hi all, Simple two part question.
1) I have a function where regexp needs to match two terms in a string.
st1='This string is going to be searched'
Expression should evaluate to True if st1 contains 'going' and 'search'.
I stole the following syntax from an old StackOverflow thread. I understand why it works. My question is, why is the '^' necessary? What is it doing?
hasMatch=~isempty(regexp(st1,'^(?=.*going).*(?=.*search).*'))
2) This code will be in a function. I would like to generalize it to any number of substrings that need to be matched. I understand varargin, but I'm not clever enough with regexp to code an arbitrary number of substrings that must be matched. Any help would be welcome.
Thanks!
-Aram
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Aram Schiffman
Aram Schiffman 2017-11-27
编辑：Aram Schiffman 2017-11-27
Right, good point. Answer is order-independent. I just need all N substrings to be matched -- somewhere.
Thanks, Aram
Stephen23
Stephen23 2017-11-27
@Aram Schiffman: a regular expression is fundamentally order-dependent. You should consider other solutions.

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Stephen23
Stephen23 2017-11-27
编辑：Stephen23 2017-11-27
You do not need to use regexp to fulfill the given requirements:
>> st1 = 'This string is going to be searched';
>> fun = @(s)~isempty(strfind(st1,s));
>> all(cellfun(fun,{'going','search'}))
ans = 1
>> all(cellfun(fun,{'going','elephant'}))
ans = 0
You can put this into a function, and provide as many inputs as you want:
function out = areinstr(str,varargin)
fun = @(s)~isempty(strfind(str,s));
out = all(cellfun(fun,varargin));
end
and tested:
>> areinstr(st1,'going','search','This')
ans = 1
>> areinstr(st1,'going','search','This','string')
ans = 1
>> areinstr(st1,'going','search','This','string','antelope')
ans = 0
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Stephen23
Stephen23 2017-11-27
"I thought there was a way for them not to beI thought there was a way for them not to be"
There are some hacks that can be used to make them order-independent, but they make expression much more complex and slow.
Remember to accept the answer that best helps you to resolve your original question. That is the easiest way to show your thanks to the volunteers who helped you.

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