1.20.3 Get methods

chain <-_arg: index=int -> any

@see object<-_arg

chain <-_arity: -> int

@see object<-_arity

chain <-cell_value: cell_reference=int -> any

Value associated with a cell. Use with care.

See also

- chain<-next_cell
- chain<-head_cell
- chain->cell_value

chain <-complete_name: prefix=char_array, extract_name=[function]*, ignore_case=[bool] -> tuple

Support the implementation of automatic completion as found with class text_item. The chain is a chain of elements from which one has to be chosen by means of completion. Prefix is the string typed so far. Extract_name is a function to extract the name from the each element. Its values are:

@nil	Use default conversion to text.
@default	Use object<-print_name.
Function	Use this function, @arg1 is the element.

The return value is a tuple object. The tuple<-first contains a new chain holding all elements of the receiving string whose name start with the given prefix. The tuple<-second contains a new string object holding the largest common prefix of all matches. If no element of the chain matches prefix, this method fails. Example:

?- get(chain(gnu, foo, gnats, bar), complete_name, 'g',
           tuple(Matches, string(Common))),
   object(Matches, Chain).

Common = gn
Chain = chain(gnu, gnats)
Matches = @854357/chain

See also text_item->complete.

chain <-convert: vector -> chain

Convert a vector object (array) into a linked list (chain object). Because a Prolog list is translated into a code_vector object, any method requiring a chain argument can be passed a Prolog list. For example:

send(new(B, browser), open),
send(B, members, [gnu, gnat, gnome]).

chain <-copy: -> chain

Creates a copy of the chain holding the same elements in the same order.

When the receiver is a subclass of chain, the resulting chain will be an instance of the same (sub)class: an instance of this subclass is created with no arguments, after which the append behaviour of class chain is used to append the elements.

Bugs: Creating copies of subclasses is ill-defined.

chain <-current: -> any

Get the value of the current cell. Use of the current field of chains is discouraged as it makes the code non-reentrant.

See also

topic Current

chain <-current_no: -> int

Get index of the current cell. Fails if the chain has no current cell. See also chain->current

See also

- topic Current
- chain<-index

chain <-find: test=code -> any

Successively executes code on the elements. Returns the first element for which code succeeds or fails. Arguments:

@arg1	Element tested
@arg2	1-based index of element

See also

- chain->for_all
- chain<-find_all
- chain->find
- hash_table<-find_key

chain <-find_all: test=code -> chain

Returns a new chain holding all elements for which the execution of code succeeds. Arguments:

@arg1	Element tested
@arg2	1-based index of element

The following example finds all inverted graphicals on the graphical device Dev:

?- get(Dev?graphicals, find_all,
           @arg1?inverted == @on, Inverted).

See also chain->for_all.

See also

- chain->for_all
- chain<-find

chain <-head_cell: -> int

@see chain<-cell_value @see chain->cell_value

chain <-index: value=any -> index=int

@see chain<-current_no

chain <-map: function -> chain

Executes obtainer or block for each element of the chain. Returns a new chain holding the resulting values of executing the code. All elements for which the execution fails are omitted. Argument forwarding:

@arg1	Element tested
@arg2	1-based index of the element

The example below returns a chain with names holding the names of all graphical objects on the graphical device.

graphical_names(Device, Names)  :-
        get(Device, graphicals, Chain),
        get(Chain, map, @arg1?name, Names).

chain <-next: [any] -> any

Returns the element right after the given argument. If the argument is not in the chain or the argument is the last member of the chain, this method fails. If the argument occurs multiple times in the chain, the next of the first appearance is returned.

For backward compatibility only, if no argument is provided, chain<-current is returned and chain<-current is moved to the next element.

See also chain<-previous, chain<-nth1, chain<-head and chain<-tail.

See also

topic Current

chain <-next_cell: cell_reference=int -> cell_reference=int

@see chain<-cell_value @see chain->cell_value

chain <-nth1: index=int -> value=any

@see chain->current_no

chain <-previous: [any] -> any

Returns the element right before the given argument. If the argument is not in the chain or the argument is the first member of the chain, this method fails. If the argument occurs multiple times in the chain, the element before the first appearance is returned. See also chain<-next, chain<-nth1, chain<-head and chain<-tail.

chain <-sub: start=int, end=[int] -> chain

Get new sub-chain from 0-based start and end. End defaults to chain<-size. The object at chain<-end is not included. Example:

?- get_object(chain(0,1,2,3), sub, 1, 2, X).

X = chain(1)

See also char_array<-sub.