Method for runtime expressions cpp?

Hey I'm looking for a light and portable lib or something that'll let me parse simple expressions at runtime with a syntax similar to c++. I need loops and conditionals, but no advanced object manip and stuff. Example:
for(i=0; i < 20; i++) {  if(i < 12) { V[i] = A*B; } else { V[i] = 0; } }

I've looked at v8, lua (though syntax is bonkers). I feel like both are also overkill. Any suggestions?

Its definitely a weird use case. I'm working on this parser that takes a bytestream from a device and converts it to a meaningful value. The expression to convert the data isn't definitive though -- it varies between between devices by make and model so I can't hardcode all the interpretations and forget about it.

I need people who aren't programmers to be able to add interpretations without compiling in an easy manner so they can support their device with minimal effort.