code-snippet-1.md

# Any expression in the language
role Expr {}
# map f v
role MapV[Expr \f_,Expr \v_] does Expr {
    has Expr $.f = f_;
    has Expr $.v = v_;
}
# function composition f . g
role Comp[Expr \f_, Expr \g_] does Expr {
    has Expr $.f = f_;
    has Expr $.g = g_;
}
# zipt t turns a tuple of vectors into a vector of tuples
role ZipT[Expr \t_] does Expr {
    has Expr $.t = t_
}
# tuples are just arrays of Expr
role Tuple[Array[Expr] \e_] does Expr {
    has Array[Expr] $.e = e_
}
# names of functions and vectors are just string constants
role Name[Str \n_] does Expr {
    has Str $.n = n_
}