Grammar for parsing natural language descriptions of a virtual machine.

§1. This nonterminal corresponds to the Inbuild version number syntax in the arch module: for example, it matches 2.7.6 or 3/990505. A bit awkwardly, because a semantic version number is stored as an actual struct rather than being created on the heap as an object: so we can't make the return value of this nonterminal a pointer to that struct, as that would be out of scope when needed. Instead, we have to wrap it up in a holder object to give it permanency. 

<version-number> internal 1 {
    TEMPORARY_TEXT(vtext)
    WRITE_TO(vtext, "%W", W);
    semantic_version_number V = VersionNumbers::from_text(vtext);
    DISCARD_TEXT(vtext)
    if (VersionNumbers::is_null(V) == FALSE) {
        semantic_version_number_holder *H = CREATE(semantic_version_number_holder);
        H->version = V;
        ==> { -, H };
        return TRUE;
    }
    ==> { fail nonterminal };
}

§2. The following nonterminal matches any valid description of a virtual machine. 

<virtual-machine> internal {
    TEMPORARY_TEXT(vtext)
    WRITE_TO(vtext, "%W", W);
    compatibility_specification *C = Compatibility::from_text(vtext);
    DISCARD_TEXT(vtext)
    if (C) {
        ==> { -, C };
        return TRUE;
    }
    ==> { fail nonterminal };
}