#default_args

compiles:
function(x=1) {

}

to:
function(x) { x = x==null ? 1 : x;

}

compiles:
function(a, x={}) {
  ax = 2
}

to:
function(a, x) { x = x==null ? {} : x;
  ax = 2
}

compiles:
function(x=1, r=[], a=3) {
  
}

to: 
function(x, r, a) { x = x==null ? 1 : x, r = r==null ? [] : r, a = a==null ? 3 : a;

}
