Реструктуризующее присваивание

Author: aNNiMON

program.own

@@ -185,4 +185,15 @@ println class.add(2, class.mul(2, 2))
 println split("1/2/3/4/5/6", "/")
 println join(nums, ", ")
 println join(nums, "|", "/")
-println join(nums, ", ", "[", "]")
+println join(nums, ", ", "[", "]")
+
+// Destructuring assignment
+arr = ["a", "b", "c"]
+extract(var1, var2, var3) = arr
+echo(var1, var2, var3)
+// Swap
+extract(var2, var1) = [var1, var2]
+echo(var1, var2)
+
+extract(, , var4) = arr
+println var4

src/com/annimon/ownlang/parser/Lexer.java

@@ -74,6 +74,7 @@ public final class Lexer {
         KEYWORDS.put("use", TokenType.USE);
         KEYWORDS.put("match", TokenType.MATCH);
         KEYWORDS.put("case", TokenType.CASE);
+        KEYWORDS.put("extract", TokenType.EXTRACT);
     }
 
     private final String input;

src/com/annimon/ownlang/parser/Parser.java

@@ -87,6 +87,9 @@ private Statement statement() {
         if (match(TokenType.MATCH)) {
             return new ExprStatement(match());
         }
+        if (match(TokenType.EXTRACT)) {
+            return destructuringAssignment();
+        }
         if (lookMatch(0, TokenType.WORD) && lookMatch(1, TokenType.LPAREN)) {
             return new ExprStatement(function(qualifiedName()));
         }
@@ -107,6 +110,22 @@ private Statement assignmentStatement() {
         throw new ParseException("Unknown statement: " + get(0));
     }
 
+    private DestructuringAssignmentStatement destructuringAssignment() {
+        // extract(var1, var2, ...) = ...
+        consume(TokenType.LPAREN);
+        final List<String> variables = new ArrayList<>();
+        while (!match(TokenType.RPAREN)) {
+            if (lookMatch(0, TokenType.WORD)) {
+                variables.add(consume(TokenType.WORD).getText());
+            } else {
+                variables.add(null);
+            }
+            match(TokenType.COMMA);
+        }
+        consume(TokenType.EQ);
+        return new DestructuringAssignmentStatement(variables, expression());
+    }
+    
     private Statement ifElse() {
         final Expression condition = expression();
         final Statement ifStatement = statementOrBlock();

src/com/annimon/ownlang/parser/TokenType.java

@@ -26,6 +26,7 @@ public enum TokenType {
     USE,
     MATCH,
     CASE,
+    EXTRACT,
 
     PLUS, // +
     MINUS, // -

src/com/annimon/ownlang/parser/ast/DestructuringAssignmentStatement.java

@@ -0,0 +1,70 @@
+package com.annimon.ownlang.parser.ast;
+
+import com.annimon.ownlang.lib.ArrayValue;
+import com.annimon.ownlang.lib.MapValue;
+import com.annimon.ownlang.lib.Types;
+import com.annimon.ownlang.lib.Value;
+import com.annimon.ownlang.lib.Variables;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+/**
+ *
+ * @author aNNiMON
+ */
+public final class DestructuringAssignmentStatement implements Statement {
+    
+    public final List<String> variables;
+    public final Expression containerExpression;
+
+    public DestructuringAssignmentStatement(List<String> arguments, Expression container) {
+        this.variables = arguments;
+        this.containerExpression = container;
+    }
+    
+    @Override
+    public void execute() {
+        final Value container = containerExpression.eval();
+        switch (container.type()) {
+            case Types.ARRAY:
+                execute((ArrayValue) container);
+                break;
+            case Types.MAP:
+                execute((MapValue) container);
+                break;
+        }
+    }
+    
+    private void execute(ArrayValue array) {
+        final int size = variables.size();
+        for (int i = 0; i < size; i++) {
+            final String variable = variables.get(i);
+            if (variable != null) {
+                Variables.set(variable, array.get(i));
+            }
+        }
+    }
+    private void execute(MapValue map) {
+        int i = 0;
+        for (Map.Entry<Value, Value> entry : map) {
+            final String variable = variables.get(i);
+            if (variable != null) {
+                Variables.set(variable, new ArrayValue(
+                        new Value[] { entry.getKey(), entry.getValue() }
+                ));
+            }
+            i++;
+        }
+    }
+    
+    @Override
+    public void accept(Visitor visitor) {
+        visitor.visit(this);
+    }
+
+    @Override
+    public String toString() {
+        return variables.toString();
+    }
+}

src/com/annimon/ownlang/parser/ast/Visitor.java

@@ -16,6 +16,7 @@ public interface Visitor {
     void visit(ConditionalExpression s);
     void visit(ContinueStatement s);
     void visit(DoWhileStatement s);
+    void visit(DestructuringAssignmentStatement s);
     void visit(ForStatement s);
     void visit(ForeachArrayStatement s);
     void visit(ForeachMapStatement s);

src/com/annimon/ownlang/parser/visitors/AbstractVisitor.java

@@ -61,6 +61,11 @@ public void visit(ConditionalExpression s) {
     @Override
     public void visit(ContinueStatement s) {
     }
+    
+    @Override
+    public void visit(DestructuringAssignmentStatement s) {
+        s.containerExpression.accept(this);
+    }
 
     @Override
     public void visit(DoWhileStatement s) {