Package com.singularsys.jep.misc.dictionary

package com.singularsys.jep.misc.dictionary
Classes to support associative array like operations.

The package provides a grammar matcher supporting a JSON like syntax for associative arrays, dictionaries or maps. 

dict = {'x':2, 'y':3}
and functions for operating on such dictionaries:
  • GetOr – getOr(dict,'x',-1) – get the value associated with a key or a default value.
  • Get – get(dict,'x') – get the value associated with a key, with configurable behaviour for missing keys.
  • ContainsKey – containsKey(dict,'x') – test if the dict contains a key.
  • Put – put(dict,'x',5) – sets the value associated with a key.
  • Remove – remove(dict,'x') – removes an entry from the table.
  • Clear – clear(dict) – clears the dict.
  • Keys – keys(dict) – returns the set of keys as a list.
  • Values – values(dict) – returns the set of values as a list.
  • Entries – entries(dict) – returns the set of entries as a doubly nested list.
  • MakeMap – hashMap(), linkedMap(), treeMap(), hashMap(list), linkedMap(list), treeMap(list) – creates maps of different types. The functions can either create empty maps, or create a map from an existing list. Each type can be used with the other methods in this package. The hashMap is unordered, linkedMap uses insertion order and treeMap sort the keys.

Three functions are defined but not implemented by default

  • EntriesIterable – entriesIter(dict) – returns an iterator for the entries.
  • KeysIterable – keysIter(dict) – returns an iterator for the keys.
  • ValuesIterable – valuesIter(dict) – returns an iterator for the values.

Some configurations allow values can be omitted in which case the map functions like a set, that can be define using set = {'x', 'y'} and added to using put('set','z') . A special value DictionaryComponents.getNullValue() is used to represent a missing value, this can be set in the constructor.

The package can be configured either to represent maps as a Map<Object,Object>. or as doubly nested Vector<Object> , when each entry is a Vector with either 2 elements, the key and value; or a single element if the value is missing.

It can be set up using the DictionaryComponents 

jep = new Jep(
    new StandardConfigurableParser(),
    new DictionaryComponents(
        DictionaryComponents.Type.MAP_MISSING_VALUES));
Or explicitly 
// Object used to represent null values
var nullValue = new Object();

// Add operators for creating maps and map entries
var ot = new StandardOperatorTable2();
var listOp = ot.getList();
Operator mapOp = new Operator(
    "map",
    new MapPfmc(),
    Operator.NARY + Operator.NOT_IN_PARSER);
Operator entryOp = new Operator(
    "entry",
    new MapPfmc.MapEntryPfmc(
      MapGrammarMatcher.Type.ALLOW_MISSING_VALUES,
      nullValue),
    Operator.NARY + Operator.NOT_IN_PARSER);

ot.addOperator(mapOp, listOp);
ot.addOperator(entryOp, listOp);

// Adds a grammar matcher for the {'x':1,'y':2} syntax
var cp = new StandardConfigurableParser();
var stm = cp.getSymbolTokenMatcher();
var colon = new SymbolToken(":");
var bopen = new SymbolToken("{");
var bclose = new SymbolToken("}");
var comma = stm.getSymbolToken(",");
stm.add(colon);
stm.add(bopen);
stm.add(bclose);
cp.addGrammarMatcher(new MapGrammarMatcher(
    MapGrammarMatcher.Type.ALLOW_MISSING_VALUES,
    bopen, bclose, colon, comma,
    mapOp, entryOp ));

// Build the Jep instance.
jep = new Jep(cp,ot);

// Add functions
jep.addFunction("get", new Get(nullValue));
jep.addFunction("getOr", new GetOr(nullValue));
jep.addFunction("containsKey", new ContainsKey());
jep.addFunction("put",
  new Put(Put.Type.ALLOW_MISSING_VALUES, nullValue));
jep.addFunction("remove",new Remove(nullValue));
jep.addFunction("clear",new Clear(nullValue));
jep.addFunction("keys", new Keys());
jep.addFunction("values", new Values(nullValue));
jep.addFunction("entries", new Entries(nullValue));
jep.addFunction("size",new Size());
jep.addFunction("hashMap", new MakeMap(MakeMap.Type.HashMap));
jep.addFunction("linkedMap", new MakeMap(MakeMap.Type.LinkedMap));
jep.addFunction("treeMap",  new MakeMap(MakeMap.Type.TreeMap));

jep.reinitializeComponents();
Since:
Jep 4.1
See Also: