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<H2><A NAME="SECTION00071000000000000000"> </A>
<A NAME="gen-types"> </A>
<BR>
Generated Data Types
</H2>
For each phylum a C data type is generated.
Its name is the same as the phylum so it can be arbitrarily used in a C
program.
Technically, it is a structure containing the attributes, a variant
selector (cf. the operator) and a union of the alternatives.
Note that this scheme allows type checking over C programs to check if a
term is constructed from the correct phyla.
An additional data type is <I>YYSTYPE</I><A NAME="1347"> </A>,
which can be used in <I>yacc</I>-generated<A NAME="1348"> </A>
parsers to construct terms.
The generated C for the example in Section <A HREF="node7.html#input-terms">1.1</A> and
Section <A HREF="node8.html#attr-terms-input">1.2</A>
is given below.
Note, it is rarely necessary to directly refer to these C structures, as function definitions
are much more convenient.
<A NAME="433"> </A><A NAME="434"> </A>
<PRE><HR><!--lgrindfile: generated_data_type_example.k 14:54 Jul 22 1996-->
<B>typedef</B> <B>enum</B> { ..., sel_Neg = 4, sel_Minus = 5, sel_Plus = 6, sel_Zero = 7,
sel_Nilexprlist = 8, sel_Consexprlist = 9, ... } kc_enum_operators;
<BR>
<B>typedef</B> <B>struct</B> kc_tag_expr *expr; <I>/* note that a `expr' is a pointer to a `struct kc_tag_expr'*/</I>
<B>typedef</B> <B>struct</B> kc_tag_exprlist *exprlist;
<BR>
<B>struct</B> kc_tag_expr {
kc_enum_operators prod_sel;
<B>union</B> {
<B>struct</B> {
expr expr_1;
} Neg;
<B>struct</B> {
expr expr_1;
expr expr_2;
} Minus;
<B>struct</B> {
expr expr_1;
expr expr_2;
} Plus;
} u;
<B>float</B> value; <I>/* an attribute */</I>
};
<BR>
<B>struct</B> kc_tag_exprlist {
kc_enum_operators prod_sel;
<B>union</B> {
<B>struct</B> {
expr expr_1;
exprlist exprlist_1;
} Consexprlist;
} u;
};
<HR></PRE>
<P>
The term processor generates a C type definition <I>boolean</I><A NAME="1349"> </A>
with constants <I>True</I><A NAME="1350"> </A>
and <I>False</I><A NAME="1351"> </A>
that have the usual C interpretation (namely <I>int</I>, 1, and 0).
<P>
The names of all the rewrite and unparse views are collected in enumeration types <I>rview</I><A NAME="1352"> </A> respectively <I>uview</I><A NAME="1353"> </A>.
Whether or not the user has used it, these types contains a value
<I>base_riew</I><A NAME="1354"> </A> respectively
<I>base_uview</I><A NAME="1355"> </A>.
<P>
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<BR><I>2000-04-17</I>
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