Is there a dictionary functionality in R

Is there a way to create a “dictionary” in R, such that it has pairs? Something to the effect of:

x=dictionary(c("Hi","Why","water") , c(1,5,4))
x["Why"]=5

I’m asking this because I am actually looking for a two categorial variables function.

So that if x=dictionary(c(“a”,”b”),c(5,2))

     x  val
1    a  5 
2    b  2 

I want to compute x1^2+x2 on all combinations of x keys

     x1 x2 val1  val2  x1^2+x2
1    a  a   5     5      30
2    b  a   2     5      9
3    a  b   5     2      27
4    b  b   2     2      6

And then I want to be able to retrieve the result using x1 and x2. Something to the effect of: get_result[“b”,”a”] = 9

what is the best, efficient way to do this?