Read-execute-print loop
A read-eval-print loop is an interactive programming environment that repeatedly reads input, evaluates or executes it, displays a result, and awaits further input.
A Pythonic Adventure: From Python basics to a working web app
A REPL is an interactive programming environment that repeatedly reads input, evaluates it, displays results, and waits for more input.
- How it is used
- Uses interactive Python to test expressions, inspect values, and try functions quickly.
- How deep it goes
- Explains the read–evaluate–print cycle through prompts and examples, but stops short of implementation internals.
- Examples
- Demonstrates print, arithmetic, string length, list length, repeated strings, and a menu-divider calculation.
- What you can do after
- Apply it via Mu editor to test Python expressions, inspect values, and check functions before using them in a program.
F# in Action: A Revised Edition of Get Programming with F#
A read-eval-print loop is an interactive environment that repeatedly reads source expressions, evaluates them, and prints their results.
- How it is used
- Supports rapid exploration of business logic, domain models, data, production code, and third-party packages before application integration.
- How deep it goes
- Explains ad hoc evaluation, immediate feedback, persistent state, and execution order, but stops short of implementation internals.
- Examples
- Uses FSI bindings, interpolated strings, reusable order data, price calculations, grouping, validation, and exploratory package work.
- What you can do after
- Apply it via F# Interactive to prototype rules, inspect data, test code, and refine experiments before moving results into applications.
Learn Haskell by Example
An execution mode in which program expressions or commands are entered and evaluated incrementally.
- How it is used
- Uses GHCi to prototype Haskell code, inspect evaluations, and experiment with syntax before completing a project.
- How deep it goes
- Demonstrates launching GHCi, loading project definitions, evaluating expressions, binding names, annotating types, and defining functions.
- Examples
- Uses arithmetic bindings, typed integers, the `square` function, and multi-line definitions as interactive demonstrations.
- What you can do after
- Apply it via GHCi and Stack to evaluate expressions, test bindings, inspect types, and prototype Haskell functions.
Read how Learn Haskell by Example explains read-execute-print loop →
Julia as a Second Language
The Julia REPL is Julia's interactive read-evaluate-print loop for entering expressions and viewing their results.
- How it is used
- Supports interactive experimentation, testing, and debugging by evaluating expressions at a command-line prompt.
- How deep it goes
- Shows launch, expression evaluation, tab completion, and shortcuts, without detailing the loop's implementation.
- Examples
- Uses arithmetic and mathematical function calls, function-name completions, and variable assignments at the `julia>` prompt.
- What you can do after
- Operate the Julia REPL to try expressions, inspect results, complete names, and interrupt or exit a session.
Read how Julia as a Second Language explains read-execute-print loop →
Clojure: The Essential Reference
A REPL is an interactive programming environment that repeatedly reads input, evaluates it, and prints the result.
- How it is used
- Provides interactive evaluation and a foundation for building specialized command-line tools.
- How deep it goes
- Explains the loop and demonstrates initialization, prompting, reading, parsing, and evaluation without detailing internal implementation.
- Examples
- Uses a calculator with named arithmetic functions and a parser for expressions such as 2*3.
- What you can do after
- Build it from scratch as a customized Clojure REPL with tailored startup, prompt, input, and evaluation behavior.
Read how Clojure: The Essential Reference explains read-execute-print loop →
Functional Programming in Scala, Second Edition
A read-eval-print loop is an interactive environment that repeatedly reads an expression, evaluates it, prints the result, and prompts for another expression.
- How it is used
- Supports interactive experimentation, source-file loading, scripting, and quick checks while programming in Scala.
- How deep it goes
- Defines the read-evaluate-print cycle and demonstrates loading and calling code, but does not explain interpreter internals.
- Examples
- Uses string reversal, mutable StringBuilder behavior, source-file loading, and an absolute-value call to illustrate interactive evaluation.
- What you can do after
- Operate the Scala interpreter to enter expressions, load definitions, inspect typed results, and exit the session.
Read how Functional Programming in Scala, Second Edition explains read-execute-print loop →
Related concepts
- interactive programmingused by · Interactive programming is a programming style that supports entering, evaluating, and revising code incrementally during an ongoing session.
- Pythonuses · Python is a high-level, general-purpose, dynamically typed programming language known for readable syntax and automatic memory management.
- mongoshincludes · mongosh is MongoDB’s interactive command-line shell for connecting to deployments and executing database commands and queries.
- Node.jsuses · Node.js is an open-source JavaScript runtime built on the V8 engine that executes JavaScript outside web browsers and provides APIs for system and network operations.
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