dereference

Calc Software Package for Number Calc

NAME
    * - dereference or indirection operator

SYNOPSIS
    * X

TYPES
    X		address or lvalue

    return	any

DESCRIPTION
    When used as a binary operator, '*' performs multiplication.  When
    used as a operator, '*' returns the value at a given address.

    If X is an address, *X returns the value at that address.  This value
    will be an octet, lvalue, string, or number, depending on the
    type of address.  Thus, for any addressable A, *&A is the same as A.

    If X is an lvalue, *X returns the current value at the address
    considered to be specified by X.  This value may be an lvalue or
    octet, in which cases, for most operations except when X is the
    destination of an assignment, *X will contribute the same as X to
    the result of the operation. For example, if A and B are lvalues
    whose current values are numbers, A + B, *A + B, A + *B and *A + *B
    will all return the same result.  However if C is an lvalue and A is
    the result of the assignment A = &C, then A = B will assign the value
    of B to A, *A = B will assign the value of B to C without affecting
    the value of A.

    If X is an lvalue whose current value is a structure (matrix, object,
    list, or association), the value returned by *X is a copy of the
    structure rather than the structure identified by X.  For example,
    suppose B has been created by

	; mat B[3] = {1,2,3}

    then

	; A = *B = {4,5,6}

    will assign the values 4,5,6 to the elements of a copy of B, which
    will then become the value of A, so that the values of A and B will
    be different.  On the other hand,

	; A = B = {4,5,6}

    will result in A and B having the same value.

    If X is an octet, *X returns the value of that octet as a number.

    The * operator may be iterated with suitable sequences of pointer-valued
    lvalues.  For example, after

	; global a, b, c;
	; b = &a;
	; c = &b;

    **c returns the lvalue a;  ***c returns the value of a.

EXAMPLE
    ; mat A[3] = {1,2,3}
    ; p = &A[0]
    ; print *p, *(p + 1), *(p + 2)
    1 2 3

    ; *(p + 1) = 4
    ; print A[1]
    4

    ; A[0] = &a
    ; a = 7
    ; print **p
    7

LIMITS
    none

LINK LIBRARY
    none

SEE ALSO
    address, isptr

## Copyright (C) 1999-2006  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
##
## @(#) $Revision: 29.4 $
## @(#) $Id: dereference,v 29.4 2006/06/10 12:28:10 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/dereference,v $
##
## Under source code control:	1997/09/06 20:03:34
## File existed as early as:	1997
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/