Select all correct statements about val form and def form definitions:
-
The def form is “by-name”, its right hand side is evaluated on each use. -
The right-hand side of a val definition is evaluated at the point of the definition itself. -
The right-hand side of a def definition is evaluated at the point of the definition itself. -
The def form is “by-value”, its right hand side is evaluated on each use. -
The val form is “by-name”, its right hand side is evaluated on each use. -
The val form is “by-value”. -
The val form is “by-name”, its right hand side is evaluated at the point of the definition itself.
Explanation
Get an explanation when it's available:
Theory
-
Function parameters can be passed by value or be passed by name.
The same distinction applies to definitions.
The def form is “by-name”, its right hand side is evaluated on each use.
There is also a val form, which is “by-value”.
Example:
The right-hand side of a val definition is evaluated at the point of the definition itself.val x = 2 val y = square(x)
Afterwards, the name refers to the value. For instance, y above refers to 4, not square(2). -
The difference between val and def becomes apparent when the right hand side does not terminate.
Given
A definitiondef loop: Boolean = loop
is OK, but a definitiondef x = loop
will lead to an infinite loop.val x = loop
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