Hello, X-flow:

After learning and reprograming the code for most of the year,I meet a problem in the "parser.c" file :

After reading the whole code line-by-line，I didn't find any problem with the

"int evaluate (char *s, double *r)" function,which transform the string-typed boundary condition into the concrete data under the "void SetBoundary ()" function. But,in practice,when the imput boundary parameters include the 'sin(x)' or ‘sqrt(x)’, the program cannot get the corresponding right boundary data.However ,when the boundary parameters include the 'cos(x-pi/2)' or ‘abs(x)’, the program do get the corresponding right boundary condition.

Do you know how to solve this problem?

Thanks for your patience to read through my questions!

Your reply is deeply-appreciated!

Best Regards!