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.\" ========================================================================
.\"
.IX Title "XS::APItest::KeywordRPN 3"
.TH XS::APItest::KeywordRPN 3 "2012-11-03" "perl v5.12.5" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
XS::APItest::KeywordRPN \- write arithmetic expressions in RPN
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&        use XS::APItest::KeywordRPN qw(rpn calcrpn);
\&
\&        $triangle = rpn($n $n 1 + * 2 /);
\&
\&        calcrpn $triangle { $n $n 1 + * 2 / }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module supplies plugged-in keywords, using the new mechanism in Perl
5.11.2, that allow arithmetic to be expressed in reverse Polish notation,
in an otherwise Perl program.  This module has serious limitations and
is not intended for real use: its purpose is only to test the keyword
plugin mechanism.  For that purpose it is part of the Perl core source
distribution, and is not meant to be installed.
.SS "\s-1RPN\s0 expression syntax"
.IX Subsection "RPN expression syntax"
Tokens of an \s-1RPN\s0 expression may be separated by whitespace, but such
separation is usually not required.  It is required only where unseparated
tokens would look like a longer token.  For example, \f(CW\*(C`12 34 +\*(C'\fR can be
written as \f(CW\*(C`12 34+\*(C'\fR, but not as \f(CW\*(C`1234 +\*(C'\fR.
.PP
An \s-1RPN\s0 expression may be any of:
.ie n .IP "1234" 4
.el .IP "\f(CW1234\fR" 4
.IX Item "1234"
A sequence of digits is an unsigned decimal literal number.
.ie n .IP "$foo" 4
.el .IP "\f(CW$foo\fR" 4
.IX Item "$foo"
An alphanumeric name preceded by dollar sign refers to a Perl scalar
variable.  Only variables declared with \f(CW\*(C`my\*(C'\fR or \f(CW\*(C`state\*(C'\fR are supported.
If the variable's value is not a native integer, it will be converted
to an integer, by Perl's usual mechanisms, at the time it is evaluated.
.ie n .IP "\fIA\fR \fIB\fR ""+""" 4
.el .IP "\fIA\fR \fIB\fR \f(CW+\fR" 4
.IX Item "A B +"
Sum of \fIA\fR and \fIB\fR.
.ie n .IP "\fIA\fR \fIB\fR ""\-""" 4
.el .IP "\fIA\fR \fIB\fR \f(CW\-\fR" 4
.IX Item "A B -"
Difference of \fIA\fR and \fIB\fR, the result of subtracting \fIB\fR from \fIA\fR.
.ie n .IP "\fIA\fR \fIB\fR ""*""" 4
.el .IP "\fIA\fR \fIB\fR \f(CW*\fR" 4
.IX Item "A B *"
Product of \fIA\fR and \fIB\fR.
.ie n .IP "\fIA\fR \fIB\fR ""/""" 4
.el .IP "\fIA\fR \fIB\fR \f(CW/\fR" 4
.IX Item "A B /"
Quotient when \fIA\fR is divided by \fIB\fR, rounded towards zero.
Division by zero generates an exception.
.ie n .IP "\fIA\fR \fIB\fR ""%""" 4
.el .IP "\fIA\fR \fIB\fR \f(CW%\fR" 4
.IX Item "A B %"
Remainder when \fIA\fR is divided by \fIB\fR with the quotient rounded towards zero.
Division by zero generates an exception.
.PP
Because the arithmetic operators all have fixed arity and are postfixed,
there is no need for operator precedence, nor for a grouping operator
to override precedence.  This is half of the point of \s-1RPN\s0.
.PP
An \s-1RPN\s0 expression can also be interpreted in another way, as a sequence
of operations on a stack, one operation per token.  A literal or variable
token pushes a value onto the stack.  A binary operator pulls two items
off the stack, performs a calculation with them, and pushes the result
back onto the stack.  The stack starts out empty, and at the end of the
expression there must be exactly one value left on the stack.
.SH "OPERATORS"
.IX Header "OPERATORS"
These are the operators being added to the Perl language.
.IP "rpn(\s-1EXPRESSION\s0)" 4
.IX Item "rpn(EXPRESSION)"
This construct is a Perl expression.  \fI\s-1EXPRESSION\s0\fR must be an \s-1RPN\s0
arithmetic expression, as described above.  The \s-1RPN\s0 expression is
evaluated, and its value is returned as the value of the Perl expression.
.IP "calcrpn \s-1VARIABLE\s0 { \s-1EXPRESSION\s0 }" 4
.IX Item "calcrpn VARIABLE { EXPRESSION }"
This construct is a complete Perl statement.  (No semicolon should
follow the closing brace.)  \fI\s-1VARIABLE\s0\fR must be a Perl scalar \f(CW\*(C`my\*(C'\fR
variable, and \fI\s-1EXPRESSION\s0\fR must be an \s-1RPN\s0 arithmetic expression as
described above.  The \s-1RPN\s0 expression is evaluated, and its value is
assigned to the variable.
.SH "BUGS"
.IX Header "BUGS"
This module only performs arithmetic on native integers, and only a
small subset of the arithmetic operations that Perl offers.  This is
due to it being intended only for demonstration and test purposes.
.PP
The \s-1RPN\s0 parser is liable to leak memory when a parse error occurs.
It doesn't leak on success, however.

.\" Oracle has added the ARC stability level to this manual page
.SH ATTRIBUTES
See
.BR attributes (5)
for descriptions of the following attributes:
.sp
.TS
box;
cbp-1 | cbp-1
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE 
=
Availability	runtime/perl-512
=
Stability	Uncommitted
.TE 
.PP
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Devel::Declare,
\&\*(L"PL_keyword_plugin\*(R" in perlapi
.SH "AUTHOR"
.IX Header "AUTHOR"
Andrew Main (Zefram) <zefram@fysh.org>
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (C) 2009 Andrew Main (Zefram) <zefram@fysh.org>
.SH "LICENSE"
.IX Header "LICENSE"
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.


.SH NOTES

.\" Oracle has added source availability information to this manual page
This software was built from source available at https://java.net/projects/solaris-userland.  The original community source was downloaded from  http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2

Further information about this software can be found on the open source community website at http://www.perl.org/.