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simple-string

simple-string Type

Supertypes:

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

Description:

A simple string is a specialized one-dimensional simple array whose elements are of type character or a subtype of type character. When used as a type specifier for object creation, simple-string means (simple-array character (size)).

Compound Type Specifier Kind:

Abbreviating.

Compound Type Specifier Syntax:

(simple-string [size])

Compound Type Specifier Arguments:

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

Compound Type Specifier Description:

This denotes the union of all types (simple-array c (size)) for all subtypes c of character; that is, the set of simple strings of size size.

Expanded Reference: simple-string​

A simple-string is a string that is a simple-array​

A simple-string is a string that is not displaced, has no fill pointer, and is not adjustable. String literals and strings from make-string are simple strings.

(typep "hello" 'simple-string)
=> T

(typep (make-string 5 :initial-element #\x) 'simple-string)
=> T

Compound type specifier with size​

The compound form (simple-string size) denotes simple strings of a specific length.

(typep "hello" '(simple-string 5))
=> T

(typep "hello" '(simple-string 3))
=> NIL

(typep "hello" '(simple-string *))
=> T

Non-simple strings​

Strings with fill pointers, adjustable strings, and displaced strings are not simple strings.

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

(typep (make-array 5 :element-type 'character
                     :adjustable t
                     :initial-element #\a)
       'simple-string)
=> NIL

Type hierarchy​

simple-string is a subtype of both string and simple-array.

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

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

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

Using simple-string-p to test​

The function simple-string-p is the predicate for this type.

(simple-string-p "hello")
=> T

(simple-string-p (make-array 5 :element-type 'character
                               :fill-pointer t
                               :initial-element #\a))
=> NIL