Evaluating an AST w/in a macro?

[pmags]

I'm trying to grok how macros work and I'm a bit confused.Is it possible to 
evaluate an AST w/in a macro? In other words once I build up an AST, can I 
evaluate it within the macro so I can apply additional procs to the results of 
the evaluation before returning the results?

For example, I'm trying to write a macro which will take this syntax and return 
two tables: 1) one mapping left values to right values and 2) the other mapping 
right values to left values.
    
    
    # Desired notation:
    
    let (a,b) = DualMap:
                       1 <-> "one"
                       2 <-> "two"
    
    # desired output
    a = {1: "one", 2: "two"}
    b = {"one":1, "two":2}
    
    
    Run

Here's what I've got so far which builds up the desired table constructors 
correctly. But now I want to call tables.toTable on the two constructed tables 
(=arrays) before returning the results. Is this possible to do w/in a macro?
    
    
    import macros, table
    
    macro DualMap(body: untyped): untyped =
      body.expectKind nnkStmtList
      
      result = newStmtList()
      var tbl1 = newTree(nnkTableConstr)
      var tbl2 = newTree(nnkTableConstr)
      
      for child in body:
        if child.kind == nnkInfix and $child[0] == "<->":
          var e1 = newColonExpr(child[1], child[2])
          var e2 = newColonExpr(child[2], child[1])
          tbl1.add(e1)
          tbl2.add(e2)
      
      result.add = newPar(tbl1, tbl2)
    # but would really like to do result.add(newPar(tbl1.toTable, tbl2.toTable))
    
    
    Run