vala/valaforstatement.vala

   1 /* valaforstatement.vala
   2  *
   3  * Copyright (C) 2006-2010  Jürg Billeter
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2.1 of the License, or (at your option) any later version.
   9
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
  18  *
  19  * Author:
  20  *      Jürg Billeter <j@bitron.ch>
  21  */
  22
  23 using GLib;
  24
  25 /**
  26  * Represents a for iteration statement in the source code.
  27  */
  28 public class Vala.ForStatement : CodeNode, Statement {
  29         /**
  30          * Specifies the loop condition.
  31          */
  32         public Expression? condition {
  33                 get {
  34                         return _condition;
  35                 }
  36                 set {
  37                         _condition = value;
  38                         if (_condition != null) {
  39                                 _condition.parent_node = this;
  40                         }
  41                 }
  42         }
  43
  44         /**
  45          * Specifies the loop body.
  46          */
  47         public Block body {
  48                 get {
  49                         return _body;
  50                 }
  51                 set {
  52                         _body = value;
  53                         _body.parent_node = this;
  54                 }
  55         }
  56
  57         private List<Expression> initializer = new ArrayList<Expression> ();
  58         private List<Expression> iterator = new ArrayList<Expression> ();
  59
  60         private Expression _condition;
  61         private Block _body;
  62
  63         /**
  64          * Creates a new for statement.
  65          *
  66          * @param cond             loop condition
  67          * @param body             loop body
  68          * @param source_reference reference to source code
  69          * @return                 newly created for statement
  70          */
  71         public ForStatement (Expression? condition, Block body, SourceReference? source_reference = null) {
  72                 this.condition = condition;
  73                 this.body = body;
  74                 this.source_reference = source_reference;
  75         }
  76
  77         /**
  78          * Appends the specified expression to the list of initializers.
  79          *
  80          * @param init an initializer expression
  81          */
  82         public void add_initializer (Expression init) {
  83                 init.parent_node = this;
  84                 initializer.add (init);
  85         }
  86
  87         /**
  88          * Returns a copy of the list of initializers.
  89          *
  90          * @return initializer list
  91          */
  92         public List<Expression> get_initializer () {
  93                 return initializer;
  94         }
  95
  96         /**
  97          * Appends the specified expression to the iterator.
  98          *
  99          * @param iter an iterator expression
 100          */
 101         public void add_iterator (Expression iter) {
 102                 iter.parent_node = this;
 103                 iterator.add (iter);
 104         }
 105
 106         /**
 107          * Returns a copy of the iterator.
 108          *
 109          * @return iterator
 110          */
 111         public List<Expression> get_iterator () {
 112                 return iterator;
 113         }
 114
 115         public override void accept (CodeVisitor visitor) {
 116                 visitor.visit_for_statement (this);
 117         }
 118
 119         public override void accept_children (CodeVisitor visitor) {
 120                 foreach (Expression init_expr in initializer) {
 121                         init_expr.accept (visitor);
 122                         visitor.visit_end_full_expression (init_expr);
 123                 }
 124
 125                 if (condition != null) {
 126                         condition.accept (visitor);
 127
 128                         visitor.visit_end_full_expression (condition);
 129                 }
 130
 131                 foreach (Expression it_expr in iterator) {
 132                         it_expr.accept (visitor);
 133                         visitor.visit_end_full_expression (it_expr);
 134                 }
 135
 136                 body.accept (visitor);
 137         }
 138
 139         bool always_true (Expression condition) {
 140                 var literal = condition as BooleanLiteral;
 141                 return (literal != null && literal.value);
 142         }
 143
 144         bool always_false (Expression condition) {
 145                 var literal = condition as BooleanLiteral;
 146                 return (literal != null && !literal.value);
 147         }
 148
 149         public override bool check (CodeContext context) {
 150                 // convert to simple loop
 151
 152                 var block = new Block (source_reference);
 153
 154                 // initializer
 155                 foreach (var init_expr in initializer) {
 156                         block.add_statement (new ExpressionStatement (init_expr, init_expr.source_reference));
 157                 }
 158
 159                 // do not generate if block if condition is always true
 160                 if (condition == null || always_true (condition)) {
 161                 } else if (always_false (condition)) {
 162                         // do not generate if block if condition is always false
 163                         body.insert_statement (0, new BreakStatement (condition.source_reference));
 164                 } else {
 165                         // condition
 166                         var if_condition = new UnaryExpression (UnaryOperator.LOGICAL_NEGATION, condition, condition.source_reference);
 167                         var true_block = new Block (condition.source_reference);
 168                         true_block.add_statement (new BreakStatement (condition.source_reference));
 169                         var if_stmt = new IfStatement (if_condition, true_block, null, condition.source_reference);
 170                         body.insert_statement (0, if_stmt);
 171                 }
 172
 173                 // iterator
 174                 var first_local = new LocalVariable (context.analyzer.bool_type.copy (), get_temp_name (), new BooleanLiteral (true, source_reference), source_reference);
 175                 block.add_statement (new DeclarationStatement (first_local, source_reference));
 176
 177                 var iterator_block = new Block (source_reference);
 178                 foreach (var it_expr in iterator) {
 179                         iterator_block.add_statement (new ExpressionStatement (it_expr, it_expr.source_reference));
 180                 }
 181
 182                 var first_if = new IfStatement (new UnaryExpression (UnaryOperator.LOGICAL_NEGATION, new MemberAccess.simple (first_local.name, source_reference), source_reference), iterator_block, null, source_reference);
 183                 body.insert_statement (0, first_if);
 184                 body.insert_statement (1, new ExpressionStatement (new Assignment (new MemberAccess.simple (first_local.name, source_reference), new BooleanLiteral (false, source_reference), AssignmentOperator.SIMPLE, source_reference), source_reference));
 185
 186                 block.add_statement (new Loop (body, source_reference));
 187
 188                 var parent_block = (Block) parent_node;
 189                 parent_block.replace_statement (this, block);
 190
 191                 return block.check (context);
 192         }
 193 }