Cognitive Scaffold

Preparing your thinking workspace

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MENTAL MODEL · M4558

Lazy Evaluation

Lazy Evaluation
Learn & MetacognitionHigh supportCognitive Science
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Version 1.0.0 · Updated 2026-07-28

CORE DEFINITION

In programming language theory, lazy evaluation, also translated as delayed evaluation or lazy computation, and also known as call-by-need, is a concept in computer programming aimed at minimizing the work the computer has to do. The most important benefit of lazy evaluation is that it can greatly optimize space complexity, thus making it easy to construct infinite data types. The opposite of lazy evaluation is eager evaluation, which is the default computation method used by most programming languages, such as C. Due to translation issues, this term has two related but distinct meanings in different contexts, which can be expressed as 'delayed evaluation' and 'minimized evaluation'. The main content of this entry is about delayed evaluation; for the latter, please refer to the entry on minimal computation.

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

In programming language theory, lazy evaluation, also translated as delayed evaluation or lazy computation, and also known as call-by-need, is a concept in computer programming aimed at minimizing the work the computer has to do. The most important benefit of lazy evaluation is that it can greatly optimize space complexity, thus making it easy to construct infinite data types. The opposite of lazy evaluation is eager evaluation, which is the default computation method used by most programming languages, such as C.

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Expressions are not evaluated at binding time, but only when first needed, and the result can be cached and reused. The mechanism is to postpone computation until necessary, avoiding useless work.

MINIMUM ACTION

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Source support: Explicit

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    zh.wikipedia.orghttps://zh.wikipedia.org/wiki/%E6%83%B0%E6%80%A7%E6%B1%82%E5%80%BCZH · Explicit
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