get-path.adoc

Get-path! datatype

Table of Contents

• 1. Abstract
• 2. Creation
• 3. Literal syntax
• 4. Evaluation Steps
• 5. Testing values
• 6. Predefined words
  • 6.1. Functions

1. Abstract

A get-path! value returns the value of a path!, unevaluated.

Get-path! is a member of the following typesets: any-block!, any-path!, series!

2. Creation

Get-path! values can be created at runtime by using a make constructor or to conversion.

>> make get-path! [foo bar baz]
== :foo/bar/baz

You can create an empty get-path of a given size by supplying an integer value as an argument to make:

>> make get-path! 10
== :

To conversion:

>> to get-path! "foo bar baz"
== :foo/bar/baz

3. Literal syntax

BNF:

<get-path-literal>  ::= :<path-literal>

<path-literal> ::= <path-head>/<selector>
<path-head>    ::= <word-literal> | <path-literal>
<selector> ::= <integer> | <word-literal> | :<word-literal> | <paren>

Parse:

get-path: [get-word! some selector]
selector: [#"/" [integer! | word! | get-word! | paren!]]

Path-head datatypes: get-word!, get-path!

Selector datatypes: integer!, word!, get-word!, paren!

4. Evaluation Steps

A get-path! value follows the same evaluation rules as path! until the selector is reached, at which point the value referred to by the selector is returned without being evaluated.

5. Testing values

Use get-path? to check if a value is of the get-path! datatype.

>> get-path? first [:foo/bar]
== true

>> get-path? quote :foo/bar
== true

Use type? to return the datatype of a given value.

>> type? first [:foo/bar]
== get-path!

>> type? quote :foo/bar
== get-path!

6. Predefined words

6.1. Functions

get-path?, to-get-path