"Evaluate function" in C++

I want to know if exists an "evaluate" function in C++ like the Matlab one.

In practise, I need a function that can interprets a string like a command line.

thanks for the answers.

If you are actually trying to "evaluate" C++ source code within a running C++ application, then basically no - it's not a feature specified by the language.

There are interpreters for subsets of C++ (e.g. CInt, Ch and UnderC) - they may be able to run your C++ program if it's a relatively simple one. Alternatively, some can be embedded within a compiled C++ program to allow some run-time source code evaluation, but with limited access to and ability to change the pre-compiled code and its variables.

It's also possible for a running program to invoke the compiler and dynamically load/link a resultant library, but this is a very unusual practice and not without performance, security and interoperability issues:

• creating a new process for the compiler, compiling and linking is a relatively resource-hungry and slow operation, but once the library's linked the new code can be executed at normal out-of-line function call speeds
• the usual issues with executing an external process
  • ensuring the path and compiler executable name can't be changed by malicious inputs to the program
  • that no malware is substituted for or infecting the compiler
  • on-the-fly source code doesn't contain statements like system(), exec(), unlink() calls, abuse network connectivity, chew unwarranted CPU/memory/descriptors etc.
• the pre-compiled C++ program can't be modified or easily/deeply probed by the newly linked code, so the main mechanisms for new behaviour must have been designed in to the pre-compiled application already: expectations for newly accessible variables, functions, and factory methods / virtual dispatch.

If you actually need something more limited, like the ability to evaluate mathematical expressions or logical predicates, possibly expressed in a C++-source style, perhaps reading or setting some of your values, then various more limited and specialised libraries and embedded interpreted are available. There are even libraries for creating such parsers, such as the boost spirit library.

Finally, interpreters for other languages - Lua, Ruby, Python, Perl, TCL etc. - may be embedded in the C++ application, sporting various approaches to interoperability and security.

You can use system(): http://linux.die.net/man/3/system