16.1

Definite Assignment and Expressions

DEFINITE ASSIGNMENT

16.1   Definite Assignment and Expressions

16.1.1   Boolean Constant Expressions

V

 is definitely assigned after any constant expression whose value is

true

 when

false.

V

 is definitely assigned after any constant expression whose value is

false

when true.

A constant expression whose value is

true

 never has the value

false

, and a

constant expression whose value is

false

 never has the value

true

, these defini 

tions are vacuously satisfied. They are helpful in analyzing expressions involving

the boolean operators

&&

,

||

, and

! (

 16.1.3,  16.1.4,  16.1.5).

16.1.2   Boolean valued Expressions

For every boolean valued expression:

If the expression has no subexpressions,

V

 is definitely assigned after the

expression iff

V

 is definitely assigned before the expression. This case applies

to literals and simple names.

Otherwise,

V

 is definitely assigned after the expression iff

V

 is definitely

assigned after the expression when true and

V

 is definitely assigned after the

expression when false.

16.1.3   The Boolean Operator

&&

V

 is definitely assigned after

a

&&

b

 when true iff

V

 is definitely assigned after

a

 when true or

V

 is definitely assigned after

b

 when true.

V

 is definitely assigned after

a

&&

b

 when false iff

V

 is definitely assigned after

a

 when false and

V

 is definitely assigned after

b

 when false.

V

 is definitely assigned before

a

 iff

V

 is definitely assigned before

a

&&

b

.

V

 is definitely assigned before

b

iff

V

 is definitely assigned after

a

 when true.

16.1.4   The Boolean Operator

||

V

 is definitely assigned after

a

||

b

 when true iff

V

 is definitely assigned after

a

 when true and

V

 is definitely assigned after

b

 when true.

V

 is definitely assigned after

a

||

b

 when false iff

V

 is definitely assigned after

a

 when false or

V

 is definitely assigned after

b

 when false.

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