/interpreter/tags/at2dist130208/src/edu/vub/at/objects/natives/grammar/AGImport.java

  1/**
  2 * AmbientTalk/2 Project
  3 * AGImport.java created on 6-mrt-2007 at 21:34:54
  4 * (c) Programming Technology Lab, 2006 - 2007
  5 * Authors: Tom Van Cutsem & Stijn Mostinckx
  6 * 
  7 * Permission is hereby granted, free of charge, to any person
  8 * obtaining a copy of this software and associated documentation
  9 * files (the "Software"), to deal in the Software without
 10 * restriction, including without limitation the rights to use,
 11 * copy, modify, merge, publish, distribute, sublicense, and/or
 12 * sell copies of the Software, and to permit persons to whom the
 13 * Software is furnished to do so, subject to the following
 14 * conditions:
 15 *
 16 * The above copyright notice and this permission notice shall be
 17 * included in all copies or substantial portions of the Software.
 18 *
 19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 26 * OTHER DEALINGS IN THE SOFTWARE.
 27 */
 28package edu.vub.at.objects.natives.grammar;
 29
 30import edu.vub.at.eval.Evaluator;
 31import edu.vub.at.eval.Import;
 32import edu.vub.at.exceptions.InterpreterException;
 33import edu.vub.at.exceptions.XIllegalArgument;
 34import edu.vub.at.objects.ATContext;
 35import edu.vub.at.objects.ATObject;
 36import edu.vub.at.objects.grammar.ATExpression;
 37import edu.vub.at.objects.grammar.ATImport;
 38import edu.vub.at.objects.natives.NATTable;
 39import edu.vub.at.objects.natives.NATText;
 40
 41import java.util.HashSet;
 42import java.util.Hashtable;
 43
 44/**
 45 *  The public interface to a native import AST component, which is of the form:
 46 * 'import <expression> (alias (symbol := symbol)+ )? (exclude symbol (, symbol)* )?'
 47 *
 48 * @see edu.vub.at.objects.grammar.ATImport
 49 *
 50 * @author tvcutsem
 51 */
 52public class AGImport extends NATAbstractGrammar implements ATImport {
 53
 54	private final ATExpression importedObjectExp_;
 55
 56	private final ATExpression aliasDeclarations_;
 57	
 58	private final ATExpression excludesDeclarations_;
 59	
 60	/**
 61	 * For efficiency purposes, the table form of the alias mapping is preprocessed
 62	 * into a hashtable format.
 63	 */
 64	private Hashtable aliasedSymbols_; // maps ATSymbols to ATSymbols
 65	
 66	/**
 67	 * For efficiency purposes, the table form of the excluded symbols is preprocessed
 68	 * into a hashset format.
 69	 */
 70	private HashSet excludedSymbols_; // contains ATSymbols
 71	
 72	/** create a new import statement. The alias and excludes declaration tables may still contain quoted expressions */
 73	public AGImport(ATExpression importedObjectExp, ATExpression aliasDeclarations, ATExpression excludesDeclarations) {
 74		importedObjectExp_ = importedObjectExp;
 75		aliasDeclarations_ = aliasDeclarations;
 76		excludesDeclarations_ = excludesDeclarations;
 77		// cannot already preprocess the import statement here, as it may contain
 78		// unquotes which need to be evaluated to symbols first
 79	}
 80	
 81	public ATExpression base_aliasedSymbols() throws InterpreterException {
 82		return aliasDeclarations_;
 83	}
 84
 85	public ATExpression base_excludedSymbols() throws InterpreterException {
 86		return excludesDeclarations_;
 87	}
 88
 89	public ATExpression base_importedObjectExpression() throws InterpreterException {
 90		return importedObjectExp_;
 91	}
 92
 93	/**
 94	 * AGIMPORT(exp,aliases,excludes).eval(ctx) =
 95	 *   import(exp.eval(ctx), ctx, preprocess(aliases), preprocess(excludes)) ;
 96	 *   NIL
 97	 */
 98	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 99		if (aliasedSymbols_ == null) {
100			aliasedSymbols_ = Import.preprocessAliases(aliasDeclarations_.asTable());
101			excludedSymbols_ = Import.preprocessExcludes(excludesDeclarations_.asTable());	
102		}
103		return Import.performImport(importedObjectExp_.meta_eval(ctx), ctx, aliasedSymbols_, excludedSymbols_);
104	}
105
106	/**
107	 * Quoting an import statement results in a new quoted import statement.
108	 * 
109	 * AGIMPORT(exp,aliases,excludes).quote(ctx) = AGIMPORT(exp.quote(ctx), aliases.quote(ctx), excludes.quote(ctx))
110	 */
111	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
112		return new AGImport(importedObjectExp_.meta_quote(ctx).asExpression(),
113							aliasDeclarations_.meta_quote(ctx).asExpression(),
114							excludesDeclarations_.meta_quote(ctx).asExpression());
115	}
116	
117	public NATText meta_print() throws InterpreterException {
118		StringBuffer expression = new StringBuffer("import " + importedObjectExp_.meta_print().javaValue);
119		if (aliasDeclarations_ != NATTable.EMPTY) {
120			expression.append(" alias ");
121			if (aliasDeclarations_.isTable()) {
122				ATObject[] aliases = aliasDeclarations_.asNativeTable().elements_;
123				// append first alias
124				printAliasBinding(expression, aliases[0].asNativeTable());
125				for (int i = 1; i < aliases.length; i++) {
126					// append rest of the aliases
127					expression.append(",");
128					printAliasBinding(expression, aliases[i].asNativeTable());
129				}
130			} else {
131				// list of aliases is a quatation
132				expression.append(aliasDeclarations_.meta_print().javaValue);
133			}
134		}
135		if (excludesDeclarations_ != NATTable.EMPTY) {
136			expression.append(" exclude ");
137			if (excludesDeclarations_.isTable()) {
138				expression.append(Evaluator.printElements(excludesDeclarations_.asNativeTable().elements_, "", ",", "").javaValue);
139			} else {
140				// list of excluded symbols is a quotation
141				expression.append(excludesDeclarations_.meta_print().javaValue);
142			}
143		}
144		
145		return NATText.atValue(expression.toString());
146	}
147	
148	private void printAliasBinding(StringBuffer buff, NATTable aliasBinding) throws InterpreterException {
149		ATObject[] binding = aliasBinding.elements_;
150		if (binding.length != 2) {
151			throw new XIllegalArgument("Alias binding of import statement is not a table of size two: " + aliasBinding.meta_print().javaValue);
152		}
153		buff.append(binding[0].meta_print().javaValue).append(" := ").append(binding[1].meta_print().javaValue);
154	}
155	
156}