Rpcalc Decls
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#Wrap on
{fH4}Declarations for {fCode}rpcalc{f}{f}

Here are the C and Bison declarations for the reverse polish notation
calculator.  As in C, comments are placed between {fEmphasis}\/\*\*\/{f}.

#Wrap off
#fCode
\/\* Reverse polish notation calculator. \*\/

%\{
\#define YYSTYPE double
\#include <math.h>
%\}

%token NUM

%% \/\* Grammar rules and actions follow \*\/
#f
#Wrap on

The C declarations section (\*Note <C Declarations=>CDeclarati>: The C Declarations Section) contains two
preprocessor directives.

The {fCode}\#define{f} directive defines the macro {fCode}YYSTYPE{f}, thus
specifying the C data type for semantic values of both tokens and groupings
(\*Note <Value Type=>ValueType>: Data Types of Semantic Values).  The Bison parser will use whatever type
{fCode}YYSTYPE{f} is defined as; if you don't define it, {fCode}int{f} is the
default.  Because we specify {fCode}double{f}, each token and each expression
has an associated value, which is a floating point number.

The {fCode}\#include{f} directive is used to declare the exponentiation
function {fCode}pow{f}.

The second section, Bison declarations, provides information to Bison about
the token types (\*Note <Bison Declarations=>BisonDecla>: The Bison Declarations Section).  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 {fCode}NUM{f}, the token
type for numeric constants.

