initial checkin of SkSL compiler

src/sksl/ast/SkSLASTPrefixExpression.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+ 
+#ifndef SKSL_ASTPREFIXEXPRESSION
+#define SKSL_ASTPREFIXEXPRESSION
+
+#include "SkSLASTExpression.h"
+#include "../SkSLToken.h"
+
+namespace SkSL {
+
+/**
+ * An expression modified by a unary operator appearing in front of it, such as '-x' or '!inside'.
+ */
+struct ASTPrefixExpression : public ASTExpression {
+    ASTPrefixExpression(Token op, std::unique_ptr<ASTExpression> operand)
+    : INHERITED(op.fPosition, kPrefix_Kind)
+    , fOperator(op.fKind)
+    , fOperand(std::move(operand)) {}
+
+    std::string description() const override {
+        return Token::OperatorName(fOperator) + fOperand->description();
+    }
+
+    const Token::Kind fOperator;
+    const std::unique_ptr<ASTExpression> fOperand;
+
+    typedef ASTExpression INHERITED;
+};
+
+} // namespace
+
+#endif