▼Sugar:   readability & convenience library
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3 Container

 (require sugar/container) package: sugar

Type-neutral functions for getting elements out of a container, or testing membership.

procedure

(get container which [end_which]) → any/c

  container : (or/c list? vector? sequence? dict? string? symbol? path?)
  which : any/c
  end_which : (or/c (and/c integer? positive?) #f) = #f
For a container that’s a dict?, retrieve the element associated with the key which. Raise an error if the key doesn’t exist.

Examples:

> (get (make-hash '((a . 1) (b . 2) (c  . 3))) 'b)

len: can’t calculate length of 2

> (get (make-hash '((a . 1) (b . 2) (c  . 3))) 'z)

get: couldn’t retrieve item z from #hash((a . 1) (c . 3) (b

. 2))

For other container types — which are all sequence-like — retrieve the element located at which. Or if the optional end_which argument is provided, retrieve the elements from which to (sub1 end_which), inclusive (i.e., make a slice). Raise an error if which or end_which is out of bounds.

Examples:

> (get '(0 1 2 3 4 5) 2)

2

> (get '(0 1 2 3 4 5) 2 4)

'(2 3)

> (get '(0 1 2 3 4 5) 100)

get: couldn’t retrieve item 100 from (0 1 2 3 4 5)

> (get '(0 1 2 3 4 5) 2 100)

get: couldn’t retrieve items 2 through 100 from (0 1 2 3 4

5)

> (get (list->vector '(0 1 2 3 4 5)) 2)

2

> (get (list->vector '(0 1 2 3 4 5)) 2 4)

'#(2 3)

> (get "purple" 2)

"r"

> (get "purple" 2 4)

"rp"

> (get 'purple 2)

'r

> (get 'purple 2 4)

'rp

When container is a path, it’s treated as a list of path elements (created by explode-path), not as a stringlike value.

Examples:

> (get (string->path "/root/foo/bar/file.txt") 1)

#<path:root>

> (get (string->path "/root/foo/bar/file.txt") 0 3)

'(#<path:/> #<path:root> #<path:foo>)

To slice to the end of container, use (len container) as the value of end_which.

Examples:

> (define xs '(0 1 2 3 4 5))
> (get xs 2 (len xs))

'(2 3 4 5)

> (get (list->vector xs) 2 (len (list->vector xs)))

'#(2 3 4 5)

> (define color "purple")
> (get color 2 (len color))

"rple"

procedure

(in? item container) → boolean?

  item : any/c
  container : (or/c list? vector? sequence? set? dict? string? symbol? path?)
Return #t if item is in container, or #f otherwise.

Examples:

> (in? 2 '(0 1 2 3 4 5))

#t

> (in? 'a '(0 1 2 3 4 5))

#f

> (in? 2 (list->vector '(0 1 2 3 4 5)))

#t

> (in? "pu" "purple")

#t

> (in? "zig" "purple")

#f

> (in? 'b (make-hash '((a . 1) (b . 2) (c  . 3))))

#t

> (in? 'z (make-hash '((a . 1) (b . 2) (c  . 3))))

#f

As with get, when container is a path, it’s treated as a list of exploded path elements, not as a stringlike value.

Examples:

> (in? "foo" (string->path "/root/foo/bar/file.txt"))

#t

> (in? "zam" (string->path "/root/foo/bar/file.txt"))

#f

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