Data Types

This is an earlier edition of the documentation. For current data types and examples, open Data and Aggregate Types.

This page introduces the everyday data found on Lispex’s S-expression surface. Lispex runs directly in the reference interpreter. Try the Playground. Lispex Vouch uses the same concrete values when it binds rule inputs and receipt transcripts.

Tip: open the Playground in a new tab and try snippets as you read.

Primitive Types

The fundamental values that appear in Lispex.

Numbers

Integers, rationals, and reals (input forms):

30
19.99
-100
42/7          ; rational input form

Booleans

Truth values are #t and #f.

#t
#f
(and #t #t)       ; ⇒ #t
(or #f #t)        ; ⇒ #t
(not #t)          ; ⇒ #f
(if #t "yes" "no") ; ⇒ "yes"

Characters

Single character values.

#\a
#\space
#\x03B1          ; Greek alpha

Strings

Represents sequences of characters, enclosed in double quotes.

"Lispex Language"
"Hello, Lispex! 👋"
""
"quote: \" \n tab: \t hex: \x41;" ; escapes

Collection Types

Lists

Ordered collections of items. Create with (list ...). The empty list literal is (). Dotted lists are allowed as input.

(list)                          ; empty
(list 1 2 3 4 5)
(list "hello" "world" "lispex")
(list 1 (list 2 3) 4)          ; nested
(1 2 3 . 4)                     ; dotted list input

Common operations live in the standard library (first/rest/length, append, map/filter, …).

Vectors

#(1 2 3)
#("a" "b" "c")

Bytevectors

Arrays of bytes (integers 0–255).

#u8(72 101 108 108 111)

Quote family

Reader shorthands to build data.

'x               ; ⇒ (quote x)
`(a ,x ,@ys b)   ; ⇒ (append (list 'a x) ys (list 'b))

Functions

Functions are first‑class. Define with lambda, or with definition sugar:

(define (add a b) (+ a b))
(add 10 20) ; ⇒ 30
(lambda (n) (+ n 1)) ; anonymous function value