[Python-Dev] Jython and bool

2002年3月10日 21:06:20 +0100

Maybe this is insightful, namely how Jython
now deals with Java methods with boolean in
their signature and overloading, and the possible
scenarios in case the PEP is approved.
Let's consider the following Java class:
public class Ex {
 public void mint(int v) {}
 public void mib(boolean b) {}
 public void mib(int v) {}
 public mbool(boolean b) {}
 boolean mtrue() { return true; }
 boolean mfalse() { return false; }
 void pass(Object o) {}
 void passBool(Boolean bo) {}
}
let ex=Ex() be an instance of Ex.
*** NOW
ex.mint(0) and ex.mint(1) do the obvious thing
ex.mib(0),ex.mib(1) call ex.mib(int v)
ex.mbool(0) and ex.mbool(1) invoke ex.mbool with false and true
ex.mbool(non-integer-non-java.lang.Boolean) fails
ex.mtrue() returns 1
ex.mfalse() return 0
which means that ex.mib(ex.mtrue()) calls ex.mib(int v).
[ to call ex.mib(boolean b) one should use ex.mib(java.lang.Boolean(value)) ]
ex.pass(0) and ex.pass(1) call ex.pass with java.lang.Integer(0) and
java.lang.Integer(1)
ex.passBool(0) and ex.passBool(1) call ex.pass with
java.lang.Boolean.FALSE and java.lang.Boolean.TRUE
*** with True and False, bool is subclass of int
A) treat True as 1, False as 0 and leave everything as above (no pain,no gain)
 that means for dispatching java methods int and bool are the same,
 possibliy ex.mtrue() returns True and ex.mfalse() returns False
B)
 ex.pass(0) and ex.pass(1) call ex.pass with
 java.lang.Integer(0) and java.lang.Integer(1).
 ex.passBool(0) and ex.passBool(1) call ex.pass with
 java.lang.Boolean.FALSE and java.lang.Boolean.TRUE
 ex.pass(False) and ex.pass(True) call ex.pass with
 java.lang.Boolean.FALSE and java.lang.Boolean.TRUE
 (plus warning in the transition phase), same for ex.passBool
 ex.mtrue()/ex.mfalse() return True/False
 ex.mbool(non-integer-non-bool-non-java.lang.Boolean) fails
 ex.mbool(0) and ex.mbool(1) invoke ex.mbool with false and true
 ex.mbool(False) and ex.mbool(True) invoke ex.mbool with false and true
 ex.mib(0),ex.mib(1) call ex.mib(int v)
 ex.mib(False) and ex.mib(True) call ex.mib(boolean b)
 issuing a warning during a transition phase [involved to issue!]
 [ex.mib with a java.lang.Boolean still calls ex.mib(boolean b) so no problem
there]
 ex.mint(0) and ex.mint(1) do the obvious thing
 ex.mint(False) and ex.mint(True)
 either fail [easy to implement] or call ex.mint with 0/1 [involved!] (?)
*** with True and False, bool disujunct from int
 ex.pass(0) and ex.pass(1) call ex.pass with java.lang.Integer(0) and
java.lang.Integer(1)
 ex.passBool(0) and ex.passBool(1) maybe should *fail* after long transition ?
 ex.pass(False) and ex.pass(True) call ex.pass with
 java.lang.Boolean.FALSE and java.lang.Boolean.True
 (plus warning in the transition phase), same for ex.passBool
 ex.mtrue()/ex.mfalse() return True/False
 ex.mbool(non-bool-non-java.lang.Boolean) and
 ex.mbool(0) and ex.mbool(1) should *fail* after long transition ?
 ex.mbool(False) and ex.mbool(True) invoke ex.mbool with false and true
 ex.mib(0),ex.mib(1) call ex.mib(int v)
 ex.mib(False) and ex.mib(True) call ex.mib(boolean b)
 issuing a warning during a transition phase [involved to issue!]
 [ex.mib with a java.lang.Boolean still calls ex.mib(boolean b) so no problem
there]
 ex.mint(0) and ex.mint(1) do the obvious thing
 ex.mint(False) and ex.mint(True) should fail after transition and
 maybe call ex.mint with 0/1 with warning during transition phase [involved!]
(?)
"maybe should *fail* after long transition ?" questions:
Very likely not, user will be very unhappy to
have to change all their
jframe.setVisible(1)
or equivalent jframe.visible = 1
So for Jython bool solves a very minor wart
with a more or less affordable transition cost and
increasing amounts of purity only make us
guilty not to able to do something with them,
for *very* practical reasons <wink>.
regards.