public override void VisitForExpression(BoundForExpression node)
{
_writer.WriteKeyword("for ");
_writer.WritePunctuation("(");
_writer.WriteIdentifier(node.Variable.Name);
_writer.WritePunctuation(" <- ");
node.LowerBound.Accept(this);
_writer.WriteKeyword(" to ");
node.UpperBound.Accept(this);
_writer.WritePunctuation(") ");
_writer.WriteLine();
WriteNestedExpression(node.Body);
}
public virtual void VisitForExpression(BoundForExpression node) => this.DefaultVisit(node);
protected override BoundExpression RewriteForExpression(BoundForExpression node)
{
/*
* convert from for to while
*
* for (x <- l to u) expr
*
* var x = l
* while(x < u) {
* expr
* continue:
* x = x + 1
* }
*/
var lowerBound = RewriteExpression(node.LowerBound);
var upperBound = RewriteExpression(node.UpperBound);
var body = RewriteExpression(node.Body);
var declareX = new BoundVariableDeclarationStatement(
node.Syntax,
node.Variable,
lowerBound
);
var variableExpression = ValueExpression(node.Syntax, node.Variable);
var condition = new BoundBinaryExpression(
node.Syntax,
variableExpression,
BoundBinaryOperator.BindOrThrow(SyntaxKind.LessThanToken, Type.Int, Type.Int),
upperBound
);
var continueLabelStatement = new BoundLabelStatement(node.Syntax, node.ContinueLabel);
var incrementX = new BoundExpressionStatement(
node.Syntax,
new BoundAssignmentExpression(
node.Syntax,
variableExpression,
new BoundBinaryExpression(
node.Syntax,
variableExpression,
BoundBinaryOperator.BindOrThrow(SyntaxKind.PlusToken, Type.Int, Type.Int),
new BoundLiteralExpression(node.Syntax, 1)
)
)
);
var whileBody = new BoundBlockExpression(
node.Syntax,
ImmutableArray.Create <BoundStatement>(
new BoundExpressionStatement(body.Syntax, body),
continueLabelStatement,
incrementX
),
new BoundUnitExpression(node.Syntax)
);
var newBlock = new BoundBlockExpression(
node.Syntax,
ImmutableArray.Create <BoundStatement>(declareX),
new BoundWhileExpression(
node.Syntax,
condition,
whileBody,
node.BreakLabel,
new BoundLabel("continue")
)
);
return(RewriteExpression(newBlock));
}
protected override BoundExpression RewriteForExpression(BoundForExpression node)
{
throw new InvalidProgramException("No `for` expression should exist at this stage");
}
