This module provides DCG compatible rules for managing a state variable which consistists of an environment, which contains a set of key-value mappings. The predicates do a number of checks to ensure safe and consistant use.

 init_env// is det

Set state to empty environment.

 key_val(?Key, ?Val)// is nondet

Enumerate all keys and associated values.

 get_key(+Key, +Default, ?Val)// is det

Unify Val with value associated with Key or Default if not present.

 get_key(+Key, ?Val)// is det

Unify Val with value associated with Key.

 set_key(+Key, ?Val)// is det

Set value associated with Key to Val.

 upd_key(+Key, ?Val1, ?Val2)// is det

Unify Val1 with value associated with Key and set new value to Val2.

 del_key(+Key)// is det

Remove Key from environment.

 sel_key(+Key, ?Val)// is det

Remove Key from environment and unify Val with its value.

 ins_key(+Key, ?Val)// is det

 ins_key(+Key)// is det

Add Key to environment with given value or unbound if no value given.

 with_key(+Key, :Phrase)// is nondet

Use Phrase to compute new value of key from old.

 with_env(:Phrase) is nondet

Run phrase with initial state equal to an empty environment.

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 key(Arg1, Arg2, Arg3)

 ins_key(Arg1, Arg2, Arg3)

 ins_keys(Arg1, Arg2, Arg3)

 sel_keys(Arg1, Arg2, Arg3)