computer science

Source (programming language)

Source (programming language) is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Source (programming language) rather than just read about it. In short: Source is a family of sublanguages of JavaScript, developed for the textbook Structure and Interpretation of Computer Programs, JavaScript Edition (SICP JS). The JavaScript sublanguages Source §1, Source §2, Source §3, and Source §4 are designed to be only expressive enough to support all examples of the respective chapter of the textbook.

Key takeaways

Source (programming language) belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Source (programming language) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Source (programming language) from memory before moving on to harder problems.

Reference excerpt

Source is a family of sublanguages of JavaScript, developed for the textbook Structure and Interpretation of Computer Programs, JavaScript Edition (SICP JS). The JavaScript sublanguages Source §1, Source §2, Source §3, and Source §4 are designed to be only expressive enough to support all examples of the respective chapter of the textbook.

Purpose and design principle During the development of SICP JS, starting in 2008, it became clear that purpose-designed sublanguages of JavaScript would contribute to the learning experience. Initially called "JediScript" and inspired by the book "JavaScript: The Good Parts" by Douglas Crockford, the Source sublanguages follow the chapters of SICP JS; each language Source §x is a sublanguage of the next language Source §(x+1). Following the minimalist approach of SICP JS, implementations of Source are expected to remove any JavaScript language features that are not included in the language specification.

Features Source §1 is a very small purely functional sublanguage of JavaScript, designed for Chapter 1 of SICP JS. Source §2 adds pairs and a list library, following the data structures theme of Chapter 2. Source §3 adds stateful constructs, and Source §4 adds support for meta-circular evaluation. Chapter 5 of SICP JS does not require language support beyond Source §4. All Source languages are properly tail recursive, as required by Chapter 1 of SICP and as specified by ECMAScript 2015.

Source Academy Since the Safari browser is ECMAScript-2015-compliant, including proper tail calls, it can serve as an implementation of all Source languages, provided that the SICP package is loaded. The Source Academy is a web-based programming environment that implements all Source languages, regardless of browser support for proper tail calls, and features various tools for the readers of SICP JS. The language implementation in the Source Academy, js-slang, is also available as a standalone environment based on Node.js.

References

External links "Source (official website)". 31 December 2021. Retrieved 25 March 2022.

Worked examples

Example 1 — a first encounter with Source (programming language)

Start with the simplest possible case. Write down what Source (programming language) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Source (programming language) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Source (programming language) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Source (programming language)

In research: Source (programming language) appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Source (programming language) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Source (programming language) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cross-platform free software, Cross-platform software, Dynamic programming languages, so understanding it makes those chapters shorter.
In everyday life: Look for Source (programming language) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Source (programming language) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Source (programming language) means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Source (programming language) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Source (programming language) in simple terms?

Why does Source (programming language) matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Source (programming language)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Source (programming language).