Which example? I've probably made too many. Depending on the example it's possible to make functions that take more than one parameter. Do you have a full list of features you want it to have? I'm guessing you want all the expressions that construct expressions have?
numbers: 22, 33, 1.66
binary operators: +-*/^
unary operators: -
functions: sqrt(x), min(x,y), max(x,y), sin(x),...etc.
Can even make it have the the conditional operator (?:), but that can be a bit trickier.
Even though I use old functions it shouldn't be confusing. I tend to follow the pattern of making local variables which i immediately set from function.param(n), which works the same as function parameters. At any rate i tend to not use c3 if i can.