0.1.0

1 files changed, 19 insertions, 2 deletions

diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -7,8 +7,25 @@
 >
 > -- Revisedⁿ Reports on the Algorithmic Language Scheme (n ≥ 3, 1986–)
 
-HaScheme is a pure, call-by-need dialect of Scheme (R7RS), embedded within
-Scheme itself. Procedures in HaScheme can be written in ways that look
+HaScheme is a library that implements a subset of the R7RS's libraries
+in a lazy way, using `force` and `delay-force`.  When HaScheme is used
+by itself, it is a lazy functional programming language with the same
+syntax as Scheme, embedded within Scheme.
+
+For instance, the following `map` implementation is both valid HaScheme
+(importing `(hascheme base)`) and Scheme (importing `(scheme base)`):
+
+    (define (map f list)
+      (if (null? list)
+          '()
+          (cons (f (car list)) (map f (cdr list)))))
+
+Since HaScheme is lazy, this function will return a promise. The
+function's body is only executed if, when attempting to `force`
+a promise containing the map, the contents of the map are needed for
+a computation.
+
+Procedures in HaScheme can be written in ways that look
 identical to regular Scheme. They do not need to be explicitly `delay`ed
 or `delay-force`ed, and they only need to `force` to reduce space usage.
 HaScheme procedures return promises which can be forced by regular