Lazy evaluation

As explained in Object-Oriented Software Design in C++

The Lazy Evaluation Principle is a design principle that delays an expensive calculation until its result is needed.

How Object-Oriented Software Design in C++ covers it

How deep it goes

Defines the principle and demonstrates synchronized representations, validity flags, and demand-triggered conversion; it stops short of general algorithms.

Examples

Uses a Date class that converts between calendar fields and Julian day numbers only when access or arithmetic requires synchronization.

What it assumes

Assumes basic classes, private state, public getters, and encapsulation while teaching demand-triggered calculation through a concrete example.

What you can do after

Apply lazy evaluation by tracking representation validity and validating each representation immediately before its use.

How it connects

Connects lazy evaluation with implementation hiding, encapsulation, getter functions, and efficient date arithmetic.

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Also explained in

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  Functional Programming in Scala, Second EditionLazy evaluation defers evaluating an expression until its value is required.
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  Fast Python: High performance techniques for large datasets
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  Tiny Python Projects: Learn coding and testing with puzzles and gamesA lazy function defers producing a result until that result is needed.
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  Functional Programming in JavaScriptAn evaluation strategy that delays computing an expression until its value is required.
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  Kotlin in Action, 2ELazy evaluation postpones computation until a result is required and can stop processing once that result is obtained.
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  Learn Haskell by ExampleLazy evaluation delays evaluating an expression until its value is required.
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  The Well-Grounded Rubyist, Fourth EditionLazy evaluation defers producing results until they are requested rather than materializing all results in advance.
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  Snowflake Data EngineeringLazy execution is an evaluation strategy that postpones running data operations until a triggering operation requires their results.
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  Python How-ToLazy evaluation is an evaluation strategy in which an operation or value is computed only when its result is needed.
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  Idiomatic RustLazy evaluation is an execution strategy that postpones computing an expression until its result is required.
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  Software Design for Python ProgrammersThe Lazy Evaluation Principle postpones a calculation until its result is required, particularly when the calculation is expensive or time-consuming.
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  Fabulous Adventures in Data Structures and AlgorithmsLaziness is an evaluation strategy that defers computation until its result is needed.

Compare how 13 books explain lazy evaluation →

Related concepts

• eager evaluationcontrasts with · Eager evaluation is an execution strategy that computes expressions or performs operations immediately rather than deferring them until their results are needed.
• sequenceused by · A sequence is an ordered collection of elements whose positions determine their order of traversal or processing.
• functional, stateless philosophyused by · Functional programming is a programming paradigm that expresses computation through the evaluation and composition of functions, typically favoring immutable data and minimizing mutable state and side effects.
• generatorimplemented by · A generator is a language construct or computation that produces values incrementally on demand, typically suspending and resuming while preserving its state.
• Daskused by · Dask is an open-source Python library for parallel and distributed computing using task graphs and scalable data structures for large or partitioned workloads.
• PySparkused by · PySpark is the Python interface to Apache Spark for distributed data processing and analytics.

This explainer was generated by Manning's knowledge graph from the text of Object-Oriented Software Design in C++. The section links point to the parts of the book it draws on.