# Lucid

> programming language

**Wikidata**: [Q3561750](https://www.wikidata.org/wiki/Q3561750)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Lucid_(programming_language))  
**Source**: https://4ort.xyz/entity/lucid

## Summary
Lucid is a declarative, dataflow programming language created in 1976. It is designed for communicating instructions to a machine through a model based on the flow of data rather than sequential control flow. The language supports multiple programming paradigms, including reactive programming and concurrent computing.

## Key Facts
- **Inception:** Lucid was created in 1976.
- **Classification:** It is an instance of a programming language, specifically categorized as a dataflow programming language and a declarative programming language.
- **Paradigms:** The language supports four distinct paradigms: declarative programming, dataflow programming, reactive programming, and concurrent computing.
- **Wikipedia Presence:** The language maintains a Wikipedia presence across five languages (English, Greek, Japanese, Korean, and Chinese).
- **Library Identifiers:** Lucid is cataloged under the Library of Congress Authority ID `sh85078737` and the National Library of Israel ID `987007538681105171`.
- **Semantic ID:** It holds a Yale LUX identifier: `concept/4dc8cf88-d263-40fc-aaa2-df7794032102`.

## FAQs
### Q: What type of programming language is Lucid?
A: Lucid is a dataflow and declarative programming language. Unlike imperative languages that specify explicit control flow, Lucid is based on the availability and flow of data.

### Q: When was Lucid created?
A: Lucid was inceptioned in 1976.

### Q: What programming paradigms does Lucid support?
A: Lucid supports declarative programming, dataflow programming, reactive programming, and concurrent computing.

### Q: How is Lucid defined in library catalogs?
A: It is formally recognized as a programming language for communicating instructions to a machine and is indexed in major libraries, such as the Library of Congress.

## Why It Matters
Lucid matters in the history of computer science as an early implementation of non-imperative programming models. By defining itself as a dataflow and declarative language, Lucid offered an alternative to the von Neumann architecture-centric languages that dominated the 1970s. It addressed the challenge of expressing computation as a network of operations that react to changing data, a concept central to modern reactive and concurrent systems.

The language is significant for its multi-paradigm approach, seamlessly blending dataflow mechanics with declarative logic. This makes it a foundational subject for understanding the evolution of languages that handle concurrency and real-time data streams. Its inclusion in multiple international encyclopedias and library authorities underscores its recognized status as a distinct, theoretical, and practical contribution to programming language design. By prioritizing the *what* (declarative) over the *how* (imperative) within a dataflow context, Lucid helped pave the way for modern functional reactive programming frameworks used in complex software systems today.

## Notable For
- **Dataflow Model:** Being a distinct example of a dataflow programming language, where execution is driven by data availability.
- **Multi-Paradigm Design:** Uniquely supporting both declarative logic and concurrent computing capabilities.
- **Historical Relevance:** Originating in 1976, representing an early exploration into non-procedural language design.
- **Formal Recognition:** Being officially cataloged by the Library of Congress and the National Library of Israel.

## Body
### Classification and Definition
Lucid is formally classified as a **programming language**, defined technically as a language for communicating instructions to a machine. Within the broader taxonomy of programming languages, it is strictly typed as an **instance_of** a *dataflow programming language* and a *declarative programming language*. This distinguishes it from imperative languages by focusing on the logic of computation and data movement rather than explicit state changes.

### Programming Paradigms
Lucid operates across four key programming paradigms:
*   **Declarative Programming:** Focuses on what the program should accomplish rather than how to accomplish it.
*   **Dataflow Programming:** Models a program as a directed graph of data flowing between operations.
*   **Reactive Programming:** Handles data streams and the propagation of changes.
*   **Concurrent Computing:** Allows multiple computations to execute during overlapping time periods.

### History and Identifiers
The language traces its **inception** to **1976**. It is tracked in various semantic web and library databases, reflecting its academic and historical relevance.
*   **Wikidata & Wikipedia:** It has a sitelink count of 5, appearing in English, Greek, Japanese, Korean, and Chinese.
*   **Library Authorities:** It is listed under the Library of Congress Authority ID `sh85078737`.
*   **Database IDs:** The language is associated with the Freebase ID `/m/0555r6` and the Yale LUX ID `concept/4dc8cf88-d263-40fc-aaa2-df7794032102`.

## References

1. [Source](https://github.com/JohnMarkOckerbloom/ftl/blob/master/data/wikimap)
2. National Library of Israel Names and Subjects Authority File