A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 3. DATAFLOW ANALYSIS 23
Coding Hint: Whenever you dene a new type t, write a string of t function,
and if it makes sense, a t of string function as well. Here, we have to
in order to implement one of the functions we need for the ForwardsTransfer
signature, but it's also a good idea in general for at least two reasons. First,
they come in handy for debugging, and second, they give you a sense of how
easy the types you've dened will be to program with.
type varmap = int × (varinfo × oekind)
let id of vm (vm : varmap) : int = fst vm
let vi of vm (vm : varmap) : varinfo = vm | > snd | > fst
let kind of vm (vm : varmap) : oekind = vm | > snd | > snd
3.1.2 Functions for pretty printing the state
One of the functions we'll need to dene for the ForwardsDataFlow functor is a function to prettyprint
the abstract state. In particular, we must dene a function that turns the abstract state into
an instance of type Pretty.doc. Functions for constructing objects of this type are dened in the
module Pretty in pretty.ml. For now, though, we'll just turn our abstract state into an OCaml
string, and then use the function Pretty.text : string → doc to obtain a doc.
let string of oekind (k : oekind) : string =
match k with
| Top → "Top"
| Odd → "Odd"
| Even → "Even"
| Bottom → "Bottom"
The string of varmap function converts a varmap tuple to a string:
let string of varmap (vm : varmap) : string =
let vi = vi of vm vm in
"("¢vi.vname¢", "¢(vm | > kind of vm | > string of oekind)¢")"
The string of varmap list converts a list of varmaps into a comma-separated list:
let string of varmap list (vml : varmap list) : string =
vml
|> L.map string of varmap
|> String.concat ", "