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87 lines
2.6 KiB
Plaintext
87 lines
2.6 KiB
Plaintext
NAME
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sizeof - number of bytes required for value
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SYNOPSIS
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sizeof(x)
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TYPES
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x any
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return integer
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DESCRIPTION
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This is analogous to the C operator sizeof for the value only.
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It attempts to assess the number of bytes in memory used to store
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a value and all of its components. Unlike memsize(x), this
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builtin does not include the size of the overhead.
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Unlike size(x), this builtin incldues the trailing \0 byte on the
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end of strings.
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For numeric values, sizeof(x) ignores the demoninator if 'x' is
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an integer. For complex values, sizeof(x) ignores the imaginary
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part if 'x' is real. Because the 0, 1 and -1 numeric values are
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shared static values, sizeof(x) reports such values as having
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0 bytes of storage.
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The number returned by sizeof(x) may be less than the actual number
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used because, for example, more memory may have been allocated for
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a string than is used: only the characters up to and including the
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first '\0' are counted in calculating the contribution of the
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string to sizeof(x).
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The number returned by sizeof(x) may be greater (and indeed
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substantially greater) than the number of bytes actually used.
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For example, after:
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a = sqrt(2);
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mat A[3] = {a, a, a};
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the numerical information for a, A[0], A[1], A[2] are stored in the
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same memory, so the memory used for A is the same as if
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its 3 elements were null values. The value returned by
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sizeof(A) is calculated as A were defined by:
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mat A[3] = {sqrt(2), sqrt(2), sqrt(2)}.
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Similar sharing of memory occurs with literal strings.
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For associative arrays, only the value part of the name/value pair
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is counted.
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The minimum value for sizeof(x) occurs for the null and error values.
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EXAMPLES
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The results for examples like these will depend to some extent on
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the system being used. The following were for an SGI R4k machine
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in 32-bit mode:
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> print sizeof(null()), sizeof(0), sizeof(3), sizeof(2^32 - 1), sizeof(2^32)
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8 68 68 68 72
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> x = sqrt(2, 1e-100); print sizeof(x), sizeof(num(x)), sizeof(den(x))
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148 108 108
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> print sizeof(list()), sizeof(list(1)), sizeof(list(1,2))
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28 104 180
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> print sizeof(list()),sizeof(list(1)),sizeof(list(1,2)),sizeof(list(1,2,3))
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28 104 180 256
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> mat A[] = {1}; mat B[] = {1,2}; mat C[] = {1,2,3}; mat D[100,100];
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> print sizeof(A), sizeof(B), sizeof(C), sizeof(D)
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124 192 260 680056
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> obj point {x,y,z}
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> obj point P = {1,2,3}; print sizeof(P)
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274
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LIMITS
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It is assumed sizeof(x) will fit into a system long integer.
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LIBRARY
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none
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SEE ALSO
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size, fsize, strlen, digits
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