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simple-base-string

simple-base-string Type

Supertypes:

simple-base-string, base-string, simple-string, string, vector, simple-array, array, sequence, t

Description:

The type simple-base-string is equivalent to (simple-array base-char (*)).

Compound Type Specifier Kind:

Abbreviating.

Compound Type Specifier Syntax:

(simple-base-string [size])

Compound Type Specifier Arguments:

size—a non-negative fixnum, or the symbol *.

Compound Type Specifier Description:

This is equivalent to the type (simple-array base-char (size)); that is, the set of simple base strings of size size.

Expanded Reference: simple-base-string​

simple-base-string is equivalent to (simple-array base-char (*))​

A simple-base-string is a simple string whose elements are of type base-char. It is both a simple-string and a base-string.

;; In SBCL, string literals have element-type CHARACTER, not BASE-CHAR
(typep "hello" 'simple-base-string)
=> NIL

(subtypep 'simple-base-string 'simple-string)
=> T
=> T

(subtypep 'simple-base-string 'base-string)
=> T
=> T

Compound type specifier with size​

The compound form (simple-base-string size) restricts to simple base-strings of a given length.

;; In SBCL, string literals are not simple-base-strings
(typep "abc" '(simple-base-string 3))
=> NIL

(typep "abc" '(simple-base-string 4))
=> NIL

(typep "abc" '(simple-base-string *))
=> NIL

String literals are typically simple-base-strings​

In most implementations, string literals are simple-base-strings because they contain only standard characters.

;; In SBCL, string literals have element-type CHARACTER
(typep "Hello, World!" 'simple-base-string)
=> NIL

Non-simple strings are not simple-base-strings​

Strings with fill pointers or that are adjustable do not qualify as simple-base-strings.

(typep (make-array 5 :element-type 'base-char
                     :fill-pointer 3
                     :initial-element #\a)
       'simple-base-string)
=> NIL

Type hierarchy​

simple-base-string sits at the intersection of simple-string and base-string.

(subtypep 'simple-base-string 'string)
=> T
=> T

(subtypep 'simple-base-string 'simple-array)
=> T
=> T

(subtypep 'simple-base-string 'sequence)
=> T
=> T