Editing Scheme (programming language) (section)

===Minimalism===
{{Main|Minimalism (computing)}}
Scheme is a very simple language, much easier to implement than many other languages of comparable [[Expressive power (computer science)|expressive power]].<ref name="easy_to_implement_scheme48">The [[Scheme 48]] implementation is so-named because the interpreter was written by Richard Kelsey and Jonathan Rees in 48 hours (August 6th{{spndash}}7th, 1986. See {{Cite web |last1=Richard Kelsey |last2=Jonathan Rees |last3=Mike Sperber |date=2008-01-10 |title=The Incomplete Scheme 48 Reference Manual for release 1.8 |url=http://s48.org/1.8/manual/manual.html |access-date=2012-08-09 |publisher=Jonathan Rees, s48.org}}</ref>  This ease is attributable to the use of [[lambda calculus]] to derive much of the syntax of the language from more primitive forms. For instance of the 23 s-expression-based syntactic constructs defined in the R5RS Scheme standard, 14 are classed as derived or library forms, which can be written as macros involving more fundamental forms, principally lambda. As R5RS (§3.1) says: "The most fundamental of the variable binding constructs is the lambda expression, because all other variable binding constructs can be explained in terms of lambda expressions."<ref name="r5rs"/>

: '''Fundamental forms''': define, lambda, quote, if, define-syntax, let-syntax, letrec-syntax, syntax-rules, set!
: '''Derived forms''': do, let, let*, letrec, cond, case, and, or, begin, named let, delay, unquote, unquote-splicing, quasiquote

Example: a macro to implement <code>let</code> as an expression using <code>lambda</code> to perform the variable bindings.

<syntaxhighlight lang="Scheme">
(define-syntax let
  (syntax-rules ()
    ((let ((var expr) ...) body ...)
      ((lambda (var ...) body ...) expr ...))))
</syntaxhighlight>

Thus using <code>let</code> as defined above a Scheme implementation would rewrite "<code>(let ((a 1)(b 2)) (+ b a))</code>" as "<code>((lambda (a b) (+ b a)) 1 2)</code>", which reduces implementation's task to that of coding procedure instantiations.

In 1998, Sussman and Steele remarked that the minimalism of Scheme was not a conscious design goal, but rather the unintended outcome of the design process. "We were actually trying to build something complicated and discovered, serendipitously, that we had accidentally designed something that met all our goals but was much simpler than we had intended....we realized that the lambda calculus—a small, simple formalism—could serve as the core of a powerful and expressive programming language."<ref name="revisited"/>