mirror of
https://github.com/lcn2/calc.git
synced 2025-08-16 01:03:29 +03:00
109 lines
3.3 KiB
Plaintext
109 lines
3.3 KiB
Plaintext
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 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: 29.2 $
|
|
## @(#) $Id: dereference,v 29.2 2000/06/07 14:02:33 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/
|