+\1f
+File: bison.info, Node: Rpcalc Decls, Next: Rpcalc Rules, Up: RPN Calc
+
+Declarations for `rpcalc'
+-------------------------
+
+ Here are the C and Bison declarations for the reverse polish notation
+calculator. As in C, comments are placed between `/*...*/'.
+
+ /* Reverse polish notation calculator. */
+
+ %{
+ #define YYSTYPE double
+ #include <math.h>
+ %}
+
+ %token NUM
+
+ %% /* Grammar rules and actions follow */
+
+ The C declarations section (*note The C Declarations Section: C
+Declarations.) contains two preprocessor directives.
+
+ The `#define' directive defines the macro `YYSTYPE', thus specifying
+the C data type for semantic values of both tokens and groupings (*note
+Data Types of Semantic Values: Value Type.). The Bison parser will use
+whatever type `YYSTYPE' is defined as; if you don't define it, `int' is
+the default. Because we specify `double', each token and each
+expression has an associated value, which is a floating point number.
+
+ The `#include' directive is used to declare the exponentiation
+function `pow'.
+
+ The second section, Bison declarations, provides information to
+Bison about the token types (*note The Bison Declarations Section:
+Bison Declarations.). Each terminal symbol that is not a
+single-character literal must be declared here. (Single-character
+literals normally don't need to be declared.) In this example, all the
+arithmetic operators are designated by single-character literals, so the
+only terminal symbol that needs to be declared is `NUM', the token type
+for numeric constants.
+
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