Contents
What are the consequences of lazy evaluation?
Lazy evaluation can lead to reduction in memory footprint, since values are created when needed. However, lazy evaluation is difficult to combine with imperative features such as exception handling and input/output, because the order of operations becomes indeterminate. Lazy evaluation can introduce memory leaks.
What is a lazy data structure?
The keyword ” lazy ” indicates that values of type ‘a stream are suspended computations that, when evaluated, yield a value of the form Cons (x, c) , where x is a value of type ‘a , and c is another value of type ‘a stream , i.e., another computation of such a value.
Where is lazy evaluation used?
Lazy evaluation is used in Unix map functions to improve their performance by loading only required pages from the disk. No memory will be allocated for the remaining pages.
Why is lazy evaluation callable by value?
The original design for Better Scheme was built around lazy evaluation as embodied in the call by need semantics. It was felt this gave many advantages including more consistency and the ability to manipulate infinite structures.
Is C++ lazy evaluation?
C++ uses by default eager evaluation. C++ has short circuit evaluation. So, C++ is a little bit lazy. If the result of a logical expression is given before the whole expression was evaluated, C++ stops to evaluate the expression.
Does Python do lazy evaluation?
Yes, Python evaluates boolean conditions lazily. The docs say, The expression x and y first evaluates x; if x is false, its value is returned; otherwise, y is evaluated and the resulting value is returned.
Which is an example of a lazy evaluation?
A common use of lazy evaluation is to create so-called infinite or lazy data structures that are “fleshed out” on demand. The following example, adapted from version 5 of the Scheme manual [ADH+98, p.28], creates a “list” of all the natural numbers: Here cons can be thought of, roughly, as a concatenation operator.
How is lazy evaluation used in ALGOL 60?
In Algol 60, subroutine headers indicate which arguments are to be passed which way; the point of call and the uses of parameters within subroutines look the same in either case. A common use of lazy evaluation is to create so-called infinite or lazy data structures that are “fleshed out” on demand.
Is the target language the same as lazy evaluation?
The metalanguage and target language can use the same language, e.g., the JavaScript code displayed in Code 5.4 implements the lazy evaluation of addition. They can also be entirely two different languages. For example, Code 5.5 shows using regular expressions in Python to perform complex string processing.
What happens if there is no indexing in a logic system?
Absence of indexing in logic programming systems will result in unnecessary backtracking, leading to poor performance. Almost all systems use some form of indexing. Specifically: Most logic programming systems use the outermost symbol of the first argument for indexing. The ALS system uses full indexing as described in [Chen et al. 1992].