/interpreter/tags/at2dist041108/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;
 43import java.util.Set;
 44
 45/**
 46 *  The public interface to a native import AST component, which is of the form:
 47 * 'import <expression> (alias (symbol := symbol)+ )? (exclude symbol (, symbol)* )?'
 48 *
 49 * @see edu.vub.at.objects.grammar.ATImport
 50 *
 51 * @author tvcutsem
 52 */
 53public class AGImport extends NATAbstractGrammar implements ATImport {
 54
 55	private final ATExpression importedObjectExp_;
 56
 57	private final ATExpression aliasDeclarations_;
 58	
 59	private final ATExpression excludesDeclarations_;
 60	
 61	/**
 62	 * For efficiency purposes, the table form of the alias mapping is preprocessed
 63	 * into a hashtable format.
 64	 */
 65	private Hashtable aliasedSymbols_; // maps ATSymbols to ATSymbols
 66	
 67	/**
 68	 * For efficiency purposes, the table form of the excluded symbols is preprocessed
 69	 * into a hashset format.
 70	 */
 71	private HashSet excludedSymbols_; // contains ATSymbols
 72	
 73	/** create a new import statement. The alias and excludes declaration tables may still contain quoted expressions */
 74	public AGImport(ATExpression importedObjectExp, ATExpression aliasDeclarations, ATExpression excludesDeclarations) {
 75		importedObjectExp_ = importedObjectExp;
 76		aliasDeclarations_ = aliasDeclarations;
 77		excludesDeclarations_ = excludesDeclarations;
 78		// cannot already preprocess the import statement here, as it may contain
 79		// unquotes which need to be evaluated to symbols first
 80	}
 81	
 82	public ATExpression base_aliasedSymbols() throws InterpreterException {
 83		return aliasDeclarations_;
 84	}
 85
 86	public ATExpression base_excludedSymbols() throws InterpreterException {
 87		return excludesDeclarations_;
 88	}
 89
 90	public ATExpression base_importedObjectExpression() throws InterpreterException {
 91		return importedObjectExp_;
 92	}
 93
 94	/**
 95	 * AGIMPORT(exp,aliases,excludes).eval(ctx) =
 96	 *   import(exp.eval(ctx), ctx, preprocess(aliases), preprocess(excludes)) ;
 97	 *   NIL
 98	 */
 99	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
100		if (aliasedSymbols_ == null) {
101			aliasedSymbols_ = Import.preprocessAliases(aliasDeclarations_.asTable());
102			excludedSymbols_ = Import.preprocessExcludes(excludesDeclarations_.asTable());	
103		}
104		return Import.performImport(importedObjectExp_.meta_eval(ctx), ctx, aliasedSymbols_, excludedSymbols_);
105	}
106
107	/**
108	 * Quoting an import statement results in a new quoted import statement.
109	 * 
110	 * AGIMPORT(exp,aliases,excludes).quote(ctx) = AGIMPORT(exp.quote(ctx), aliases.quote(ctx), excludes.quote(ctx))
111	 */
112	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
113		return new AGImport(importedObjectExp_.meta_quote(ctx).asExpression(),
114							aliasDeclarations_.meta_quote(ctx).asExpression(),
115							excludesDeclarations_.meta_quote(ctx).asExpression());
116	}
117	
118	public NATText meta_print() throws InterpreterException {
119		StringBuffer expression = new StringBuffer("import " + importedObjectExp_.meta_print().javaValue);
120		if (aliasDeclarations_ != NATTable.EMPTY) {
121			expression.append(" alias ");
122			if (aliasDeclarations_.isTable()) {
123				ATObject[] aliases = aliasDeclarations_.asNativeTable().elements_;
124				// append first alias
125				printAliasBinding(expression, aliases[0].asNativeTable());
126				for (int i = 1; i < aliases.length; i++) {
127					// append rest of the aliases
128					expression.append(",");
129					printAliasBinding(expression, aliases[i].asNativeTable());
130				}
131			} else {
132				// list of aliases is a quatation
133				expression.append(aliasDeclarations_.meta_print().javaValue);
134			}
135		}
136		if (excludesDeclarations_ != NATTable.EMPTY) {
137			expression.append(" exclude ");
138			if (excludesDeclarations_.isTable()) {
139				expression.append(Evaluator.printElements(excludesDeclarations_.asNativeTable().elements_, "", ",", "").javaValue);
140			} else {
141				// list of excluded symbols is a quotation
142				expression.append(excludesDeclarations_.meta_print().javaValue);
143			}
144		}
145		
146		return NATText.atValue(expression.toString());
147	}
148	
149	private void printAliasBinding(StringBuffer buff, NATTable aliasBinding) throws InterpreterException {
150		ATObject[] binding = aliasBinding.elements_;
151		if (binding.length != 2) {
152			throw new XIllegalArgument("Alias binding of import statement is not a table of size two: " + aliasBinding.meta_print().javaValue);
153		}
154		buff.append(binding[0].meta_print().javaValue).append(" := ").append(binding[1].meta_print().javaValue);
155	}
156	
157	/**
158	 * FV(import objExp alias nam1 := nam2 exclude nam3) = FV(objExp)
159	 */
160	public Set impl_freeVariables() throws InterpreterException {
161        return importedObjectExp_.impl_freeVariables();
162	}
163	
164	
165	public Set impl_quotedFreeVariables() throws InterpreterException {
166		Set qfv = importedObjectExp_.impl_quotedFreeVariables();
167		qfv.addAll(aliasDeclarations_.impl_quotedFreeVariables());
168		qfv.addAll(excludesDeclarations_.impl_quotedFreeVariables());
169		return qfv;
170	}
171	
172}