Parameterized module for printing predicates as boolean strings

[gsingh93]

I have this code which is able to print simple predicates as boolean strings:

signature predicate pred0();

module Pred<pred0/0 p> {
  string toString() { if p() then result = "true" else result = "false" }
}

predicate foo() { any() }

predicate bar() { none() }

select Pred<foo/0>::toString(), Pred<bar/0>::toString() // result: true, false

Is it possible to generically do this for class methods that take no arguments? For example:

import semmle.code.java.frameworks.android.Android

from AndroidComponent c
select c, Pred<c.isExported>::toString()

Or maybe:

import semmle.code.java.frameworks.android.Android

from AndroidComponent c
select c, Pred<AndroidComponent, isExported>::toString(c)

My guess is no, but I wanted to confirm.

[jketema]

Hi @gsingh93,

This is indeed not possible. If you want something like this, you'll need to create a new predicate that doesn't live in a class, e.g.,

predicate isExported(AndroidComponent c) {
  c.isExported()
}

and change the signature and module to something like:

signature predicate pred0(AndroidComponent c);

module Pred<pred0/1 p> {
  string toString(AndroidComponent c) { if p(c) then result = "true" else result = "false" }
}