Parsing text without eval
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Hello,
I have some strings with values that I would like to parse. The easiest way is to use the eval function. However, I can not use it since the code is going to be compiled. Any idea on how to do this without having to parse each of the characters?
As an example, one of the string could be like this:
>> text = '{[1 2], [3 4] ''someText'' {5, [6, 7]}}'
text =
{[1 2], [3 4] 'someText' {5, [6, 7]}}
>> eval(text)
ans =
1×4 cell array
[1×2 double] [1×2 double] 'someText' {1×2 cell}
Thank you in advance!
2 Kommentare
Rik
am 21 Mär. 2023
Your requirements seem to conflict. You want to evaluate arbitrary code, but you don't want to use the function that evaluates arbitrary code.
Even if you use the recently introduced option to restrict what str2num does (to make it safer than eval) it will fail on more complicated things like you posted.
text = '{[1 2], [3 4] ''someText'' {5, [6, 7]}}'
X = str2num(text,Evaluation="restricted")
I suspect you will have to write you own parser.
Antworten (2)
Adam Danz
am 21 Mär. 2023
You could write the string to an m-file and then run the m-file, though this has the same flaws/risks as eval.
This demo creates a file temp.m, writes the string text to the file, runs the file, and then deletes the temporary file.
text = '{[1 2], [3 4] ''someText'' {5, [6, 7]}}'
tempFile = 'temp.m';
fid = fopen(tempFile,'w');
fidCleanup = onCleanup(@()fclose(fid));
fprintf(fid,'%s',text);
clear fidCleanup
run(tempFile)
delete(tempFile)
Result
ans =
1×4 cell array
{[1 2]} {[3 4]} {'someText'} {1×2 cell}
4 Kommentare
Adam Danz
am 21 Mär. 2023
Yeah, this wouldn't work outside of MATLAB. I missed that you were compiling your code.
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