hash-star

8.12

hash-star🔗ℹ

This package provides additional functions for interacting with hash tables, specifically nested hash tables.

procedure
(hash-ref* ht key ... [#:else default]) → any
  ht : hash?
  key : any/c
  default : (or/c procedure? #f) = #f

Traverses through the given hash table "ht" with the "key"s in order. If at any point, a key isn’t contained in a traversed hash table, or traversal cannot progress because a value wasn’t a hash table, the function will error. A default value or substitute error can replace the default error by passing in a lambda into the "#:else" keyword.

Examples:

> (hash-ref* (hash 'a 5))
'#hash((a . 5))
> (hash-ref* (hash 'a 5) 'a)
5
> (hash-ref* (hash 'a (hash 'b 6)) 'a)
'#hash((b . 6))
> (hash-ref* (hash 'a (hash 'b 6)) 'a 'b)
6
> (hash-ref* (hash 'a (hash 'b 6)) 'a 'b 'c)
hash-ref*: no value found for key 'c that is 2 layers deep
> (hash-ref* (hash 'a (hash 'b 6))
'a 'b 'c
#:else (thunk #f))
#f

procedure
(hash-keys-set* ht key ... val) → hash?
  ht : hash?
  key : any/c
  val : any/c

Traverses through the given hash table "ht" with the "key"s in order, creating new nested hash tables if necessary, and setting the last key to the given value.

Examples:

> (hash-keys-set* (hash) 'a 5)
'#hash((a . 5))
> (hash-keys-set* (hash 'a 5) 'a 6)
'#hash((a . 6))
> (hash-keys-set* (hash 'a (hash 'b 5)) 'a 'b 6)
'#hash((a . #hash((b . 6))))
> (hash-keys-set* (hash 'a (hash 'b 5)) 'a 'c 8)
'#hash((a . #hash((b . 5) (c . 8))))
> (hash-keys-set* (hash) 'a 'b 'c 'd)
'#hash((a . #hash((b . #hash((c . d))))))