The output is
ABC, without a newline. The relevant Scala trait linearization is D,C,B,A. Calling d.m starts with C.m, whose super.m continues to B.m, then to A.m. The latter prints A; returning through the two method bodies then prints B followed by C. The braces keep each final print inside that object method.The output becomes
BCA, without a newline. Here each method body consists only of super.m; the semicolon ends that definition. The following print("B") or print("C") is a separate statement in the trait body, so it executes during construction.Creating
new D initializes the shared base and then the B and C mixins, printing BC. The subsequent d.m still forwards along C,B,A, but only A.m now prints anything, appending A. Thus it is the placement of the construction-time statements, not a changed Scala trait linearization, that changes the output. [ref]Class inheritance defines a software class by extending another software class, inheriting its available operations and optionally adding members or providing method overriding. In languages supporting it, traits and mixins can contribute reusable behavior as well.
Use inheritance for a sound specialization whose instances can satisfy the superclass's contract wherever its instances are expected. For example, every specific gate in part (d) is usable through the common gate object interface. Subtyping supports this substitution and dynamic dispatch selects the specialized calculation. Merely noticing shared code does not establish the required behavioral relationship; object composition is often better for a replaceable component or policy that an object contains. A subclass must preserve the superclass's promised behavior, rather than just sharing its field names.
The two writable inputs and Boolean query belong to an abstract class; each concrete logic gate overrides just that query:All three subclasses satisfy the same object interface, so the
abstract class Gate {
var inp1: Boolean = false
var inp2: Boolean = false
def evalGate: Boolean
}
class OrG extends Gate {
override def evalGate: Boolean = inp1 || inp2
}
class AndG extends Gate {
override def evalGate: Boolean = inp1 && inp2
}
class XorG extends Gate {
override def evalGate: Boolean = inp1 ^ inp2
}Gate declarations in the supplied simulator still allow access to inputs and invoke the correct Boolean function through dynamic dispatch. Boolean ^ is exclusive or; || is Boolean disjunction and && is Boolean conjunction.The program first sets both inputs of Those are the two output lines. This is a simulation of combinational logic in an order where each gate's inputs have already been calculated; the Boolean assignments copy values rather than create live wire connections.
y, so . It sets . Therefore and , givingx: true
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