using symbolic calculus on char strings (coming from a file)

Hello, I'm currently using str2sym on char strings obtained from fgetl on a text file containing many lines of mathematical expressions that don't use Matlab syntax. More precisely, I perform some simple manipulations on those raw text strings (using regexprep for example), then I convert them using str2sym to make some simplifications, and I finally need to convert back the symbolic expressions to standard char strings in order to write them on a .m file (for later use). Two problems arise :

• a warning arises when using str2sym ;
• I don't know how to convert back the symbolic expressions to standard char strings

Can somebody help me ? Thanks in advance.

[madhan ravi]

can you upload a sample and your full code

[genevois pierre]

Here are samples of input file (exampleinputfile.txt) and code (treatment.m). This code relies on a function 'sym2str' that does not exist in Matlab ... And it is still under development : once my problem will be solved, i'll be able to develop lines coming after the else statement (line 134) using symbolic calculations and conversions of the results into char strings. Thank you for your help.

[madhan ravi]

Undefined function or variable 'srclines'.
Error in COMMUNITY (line 16)
while isrclines <= numel(srclines) 

[genevois pierre]

I apologize for having sent a wrong code ; here is a corrected version. Thank you for your help.

[Walter Roberson]

? str2sym does exist in MATLAB starting from r2017b which is your release .

If you have a scalar sym variable to convert back to character then use char()

If you have a nonscalar sym variable then arrayfun @char with uniform 0 . You use that instead of char() of the whole array because char applied to the whole array willl return a character vector that starts with aa call to matrix() which has to do with internal representation of the array .

Answer 1

[genevois pierre]

Thank you for your answer ; a warning when using str2sym could mean that this function will be removed in a future version ? However, I think the question can be closed now ...

[Walter Roberson]

there are warnings in r2017b about using sym() for converting expressions to symbolic but sym2var was new in that release and would not have a warning . Well just maybe in the case where the character vector was in mupad syntax , I would have to test that .