Transformation of Applicative Specifications into Imperative ...

9.4. THE TRANSFORMER
The classes in the rsllib package containing functionality for sets, lists and
maps are not altered. The list functionality is used when implementing the
transformer.
9.4 The Transformer
The result of the process described above is a transformer, which can transform
a transformable applicative RSL specification into an imperative RSL
specification according to the transformation rules given in Chapter 6. If
the applicative specification not is transformable or not within RSLA this is
reported to the user through error messages.
The transformation is done in 3 steps as shown in Figure 9.5. First of
all the applicative RSL specification is transformed into the corresponding
RSL AST using the lexer and parser. The RSL AST is transformed into an
imperative version of the RSL AST. Finally, the RSL AST is turned into an
imperative RSL specification using the string visitor StringRSLAstVisitor.java.
Applicative RSL
specification
RSLLexer
RSLParser
AST of applicative
RSL specification
TransformerRSL1
StringRSLAstVisitor
AST of imperative
RSL specification
Figure 9.5: The flow of a transformation
9.5 The Lexer and Parser
Imperative RSL
specification
The lexer and parser which transforms an RSL ASCII file into an RSL AST
is made using the ANTLR tool, [Par]. This tool generates a lexer and a
parser in Java based on a grammar file. The grammar file can be found in
Appendix E. The grammar file contains both the grammar of the lexer and
the parser.
The lexer performs a lexical analysis of the specification, which means
that it reads the specification and turns it into tokens. The parser then
determines the syntactic structure of these tokens and turns them into an
RSL AST if the parsing is successful.
The specification of the parser very much resembles that of a BNF grammar.
The grammar is built according to the syntax of RSL, which is illustrated
in Example 9.1. The example shows the part of the parser grammar
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