# FindBISON

Find `bison` executable and provide a macro to generate custom build rules.

The module defines the following variables:

`BISON_EXECUTABLE`
  path to the `bison` program
`BISON_VERSION`
  version of `bison`
`BISON_FOUND`
  true if the program was found

The minimum required version of `bison` can be specified using the standard CMake syntax, e.g. `find_package(BISON 2.1.3)`.

If `bison` is found, the module defines the macro:

    BISON_TARGET(<Name> <YaccInput> <CodeOutput>
                 [COMPILE_FLAGS <flags>]
                 [DEFINES_FILE <file>]
                 [VERBOSE <file>]
                 )

which will create a custom rule to generate a parser. `<YaccInput>` is the path to a yacc file. `<CodeOutput>` is the name of the source file generated by bison. A header file is also be generated, and contains the token list.

The options are:

`COMPILE_FLAGS <flags>`
  Specify flags to be added to the `bison` command line.
`DEFINES_FILE <file>`
  Specify a non-default header `<file>` to be generated by `bison`.
`VERBOSE <file>`
  Tell `bison` to write verbose descriptions of the grammar and parser to the given `<file>`.

The macro defines the following variables:

`BISON_<Name>_DEFINED`
  true is the macro ran successfully
`BISON_<Name>_INPUT`
  The input source file, an alias for <YaccInput>
`BISON_<Name>_OUTPUT_SOURCE`
  The source file generated by bison
`BISON_<Name>_OUTPUT_HEADER`
  The header file generated by bison
`BISON_<Name>_OUTPUTS`
  The sources files generated by bison
`BISON_<Name>_COMPILE_FLAGS`
  Options used in the `bison` command line

Example usage:

    find_package(BISON)
    BISON_TARGET(MyParser parser.y ${CMAKE_CURRENT_BINARY_DIR}/parser.cpp
                 DEFINES_FILE ${CMAKE_CURRENT_BINARY_DIR}/parser.h)
    add_executable(Foo main.cpp ${BISON_MyParser_OUTPUTS})