This library allows the creation and use of JavaScript-style objects (JSOs), which are chained mappings, represented using a variant of alists, that map keys (which must be symbols) to arbitrary values.
When you create a JSO, you can specify a prototype JSO. The recursive sequence of a JSO's prototype, the prototype of its prototype, and so on, is called the prototype chain. If a JSO doesn't contain a particular key, the prototype chain will be searched for it. Modifications, however, are only applied to the JSO proper, never to anything along the prototype chain. An attempt to look up an unknown key returns (by default) a unique value known as the undefined value, which can be tested with jso-undef?. Note that this value is not itself a JSO. A JSO without a prototype chain is called a free JSO.
A JSO is represented as a Scheme pair whose car is the symbol @ and whose cdr is the concatenation of zero or more two-element lists with another JSO or the empty list. The first element of each two-element list is a symbol known as the key and the second element is an arbitrary Scheme object known as the value. It is no accident that the attribute list of an SXML element has the same representation as a JSO.
(jso-undef obj)
Returns #t if obj is the undefined value, and #f otherwise. The undefined value is distinct in the sense of eqv? from every other Scheme object.
jso-null?
A variable whose value is the null JSO, a unique free JSO with no keys or values. It is an error to mutate the null JSO in any way.
(jso-null? obj)
Returns #t if ''obj'' is the null JSO and #f` otherwise.
(make-jso prototype obj ...)
Returns a newly allocated JSO with the specified prototype. If prototype is the undefined object, the JSO is free. Additional arguments are alternating keys and values of the JSO.
(alist->jso alist prototype)
Creates a newly allocated JSO with the specified prototype (or a free JSO if prototype is the undefined value). The key-value pairs of alist become the corresponding keys and values of the JSO.
`(jso->alist jso)
Creates a newly allocated alist whose key-value pairs are the keys and values of the JSO. The prototype chain is left unexamined.
`(full-jso->alist jso)
Creates a newly allocated alist whose key-value pairs are the keys and values of the JSO, including its prototype chain.
(jso? obj)
Returns #t if the car of jso is the symbol @, and #f otherwise. The rest of the JSO is left unexamined.
(jso-ref jso key [ failure [ success ] ])
Searches 'jso', including the prototype chain, for the key key, invokes the procedure success on it, and returns the result. If key is not found, invokes the thunk failure and returns the result. If success is not specified, it is the identity function; if fail is not specified, it is a procedure that returns the undefined value.
(jso-set! jso key value)
Searches jsofor the key key, and if found changes its value to value. If key is not found, key and value are added as the last key before the prototype chain. The prototype chain is left unexamined. Returns an undefined value (not necessarily the undefined value).
(jso-delete! jso key ...)
Searches jso and removes any key-value pairs whose key is equal to any of the keys. The prototype chain is left unexamined. Unknown keys are ignored. Returns an undefined value (not necessarily the undefined value).
(jso-delete-all! jso key-list)
Does the same as jso-delete!, except that the keys to be deleted are specified as a list.
(jso-prototype jso)
Returns the prototype of jso, or the undefined value if jso is free.
(jso-set-prototype jso prototype)
Replaces the prototype of jso with prototype. If prototype is the undefined value, jso becomes free.
(jso-contains? jso key)
Returns #t if jso contains key, and #f otherwise. The prototype chain is left unexamined.
(jso-keys jso)
Returns a list of the keys of jso. The prototype chain is left unexamined.
(jso-values jso)
Returns a list of the values of jso in the same order as jso-keys returns the keys. The prototype chain is left unexamined.
(jso-empty? jso)
Returns #t if the JSO has no keys, and #f otherwise. The prototype chain is left unexamined.
(jso-size jso)
Returns the number of keys in jso as an exact integer. The prototype chain is left unexamined.
(jso-copy jso)
Returns a copy of jso, sharing the same prototype chain. The keys and values are shared, but not the structural pairs.
(jso-full-copy jso)
Returns a copy of jso, including the prototype chain. The keys and values are shared, but not the structural pairs.
(jso-map proc jso)
Returns a newly allocated JSO after applying proc to each key and value of jso. The prototype chains are shared.
(jso-map! proc jso)
Mutates jso by applying proc to each value. The prototype chain is left unexained.
(jso-full-map proc jso)
Returns a newly allocated JSO after applying proc to each key, including those in the prototype chain.
(jso-for-each proc jso)
Applies proc to each key and value. The prototype chain is left unexamined. Returns an undefined value (not necessarily the undefined value).
(jso-full-for-each proc jso)
Applies proc to each key and value, including those in the prototype chain. Returns an undefined value (not necessarily the undefined value).
(jso-apply jso key argument ...)
Applies the result of (jso-ref jso key) on jso and the arguments, returning the result. If the result does not exist or is not a procedure, it is an error.(jso-apply jso key argument ...)
(jso-apply/fallback jso key failure argument ...)
Applies the result of (jso-ref jso key) on jso and the arguments, returning the result. If the result does not exist, the thunk failure is invoked. If the result is not a procedure, it is an error.