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83 lines
2.2 KiB
Plaintext
83 lines
2.2 KiB
Plaintext
NAME
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* - dereference or indirection operator
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SYNOPSIS
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* X
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TYPES
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X address or lvalue
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return any
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DESCRIPTION
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When used as a binary operator, '*' performs multiplication. When
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used as a operator, '*' returns the value at a given address.
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If X is an address, *X returns the value at that address. This value
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will be an octet, lvalue, string, or number, depending on the
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type of address. Thus, for any addressable A, *&A is the same as A.
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If X is an lvalue, *X returns the current value at the address
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considered to be specified by X. This value may be an lvalue or
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octet, in which cases, for most operations except when X is the
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destination of an assignment, *X will contribute the same as X to
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the result of the operation. For example, if A and B are lvalues
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whose current values are numbers, A + B, *A + B, A + *B and *A + *B
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will all return the same result. However if C is an lvalue and A is
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the result of the assignment A = &C, then A = B will assign the value
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of B to A, *A = B will assign the value of B to C without affecting
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the value of A.
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If X is an lvalue whose current value is a structure (matrix, object,
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list, or association), the value returned by *X is a copy of the
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structure rather than the structure identified by X. For example,
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suppose B has been created by
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mat B[3] = {1,2,3}
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then
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A = *B = {4,5,6}
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will assign the values 4,5,6 to the elements of a copy of B, which
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will then become the value of A, so that the values of A and B will
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be different. On the other hand,
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A = B = {4,5,6}
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will result in A and B having the same value.
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If X is an octet, *X returns the value of that octet as a number.
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The * operator may be iterated with suitable sequences of pointer-valued
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lvalues. For example, after
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> global a, b, c;
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> b = &a;
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> c = &b;
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**c returns the lvalue a; ***c returns the value of a.
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EXAMPLE
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> mat A[3] = {1,2,3}
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> p = &A[0]
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> print *p, *(p + 1), *(p + 2)
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1 2 3
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> *(p + 1) = 4
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> print A[1]
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4
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> A[0] = &a
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> a = 7
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> print **p
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7
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LIMITS
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none
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LIBRARY
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none
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SEE ALSO
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address, isptr
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