Variable size/Set

Variable size/Set
You are encouraged to solve this task according to the task description, using any language you may know.

Demonstrate how to specify the minimum size of a variable or a data type.

Ada

<lang ada>type Response is (Yes, No); -- Definition of an enumeration type with two values for Response'Size use 1; -- Setting the size of Response to 1 bit, rather than the default single byte size</lang>

AutoHotkey

The documentation explains how the built-in function VarSetCapacity() may be used to do so.

BASIC

Numerical values and arrays generally are a fixed size. Strings are dynamically resized according to the data that they hold.

Variable sizes are in chunks relating to the type of data that they contain. There may also be additional bytes of storage in the variable table that do not show in the dimensions. Typically, strings are allocated in single characters (bytes), so C$(12) in the following example is stored as 12 bytes + additional bytes used for the header in the variable table. In some implementations of basic (such as those that support the storage of variable length strings in arrays), additional terminator characters (such as a trailing Ascii NUL) may also be included. In traditional basic, integers are typically 2 bytes each, so A%(10) contains 10 lots of 2 bytes (20 bytes in total) + additional bytes used for header data in the variable table. Floating point values are typically 8 bytes each, so B(10) holds 10 lots of 8 bytes (80 bytes in total) + additional bytes for header in the variable table:

<lang basic>10 DIM A%(10): REM the array size is 10 integers 20 DIM B(10): REM the array will hold 10 floating point values 30 DIM C$(12): REM a character array of 12 bytes</lang>

BBC BASIC

Works with: BBC BASIC for Windows

The only way to 'set' the size of a scalar numeric variable is to declare it with the appropriate type suffix: <lang bbcbasic> var& = 1 : REM Variable occupies 8 bits

     var% = 1 : REM Variable occupies 32 bits
     var  = 1 : REM Variable occupies 40 bits
     var# = 1 : REM Variable occupies 64 bits</lang>

If the task is talking about setting the size of a variable at run time that is only possible with strings, arrays and structures.

C

Works with: C99

<lang c>#include <stdint.h>

int_least32_t foo;</lang>

Here foo is a signed integer with at least 32 bits. stdint.h also defines minimum-width types for at least 8, 16, 32, and 64 bits, as well as unsigned integer types.

C++

Works with: C++11

or

Works with: Boost

<lang Cpp>#include <boost/cstdint.hpp>

boost::int_least32_t foo;</lang>

D

In D, any variables of static array of zero length has a size of zero. But such data is useless, as no base type element can be accessed. <lang d>typedef long[0] zeroLength ; writefln(zeroLength.sizeof) ; // print 0</lang> NOTE: a dynamic array variable's size is always 8 bytes, 4(32-bit) for length and 4 for a reference pointer of the actual storage somewhere in runtime memory.
The proper candidates of minimum size variable are empty structure, 1-byte size data type variable (include byte, ubyte, char and bool), and void, they all occupy 1 byte. <lang d>byte b ; ubyte ub ; char c ; bool t ;</lang> bool is logically 1-bit size, but it actually occupy 1 byte.
void can't be declared alone, but void.sizeof gives 1.
An empty structure is logically zero size, but still occupy 1 byte. <lang d>struct Empty { } writefln(Empty.sizeof) ; // print 1</lang>

Fortran

Since Fortran 90 each intrinsic data type (INTEGER, REAL, COMPLEX, LOGICAL and CHARACTER) has a KIND parameter associated with it that can be used to set the required level of precision. The actual values which these KIND parameters can take are not specified in the standard and are implementation-dependent. In order to select an appropriate KIND value that is portable over different platforms we can use the intrinsic functions SELECTED_REAL_KIND and SELECTED_INT_KIND.

The syntax of these functions are as follows:-

selected_real_kind(P, R), where P is the required number of significant decimal digits and R is the required decimal exponent range. At least one argument must be present. The return value is the kind type parameter for real values with the given precision and/or range. A value of -1 is returned if P is out of range, a value of -2 is returned if R is out of range and a value of -3 is returned if both P and R are out of range.

selected_int_kind(R), where R is the required decimal exponent range. The return value is the kind type parameter for integer values n such that -10^R < n < 10^R. A value of -1 is returned if R is out of range.

<lang fortran>program setsize implicit none

 integer, parameter :: p1 = 6
 integer, parameter :: p2 = 12
 integer, parameter :: r1 = 30
 integer, parameter :: r2 = 1000
 integer, parameter :: r3 = 2
 integer, parameter :: r4 = 4
 integer, parameter :: r5 = 8
 integer, parameter :: r6 = 16
 integer, parameter :: rprec1 = selected_real_kind(p1, r1) 
 integer, parameter :: rprec2 = selected_real_kind(p2, r1) 
 integer, parameter :: rprec3 = selected_real_kind(p2, r2) 
 integer, parameter :: iprec1 = selected_int_kind(r3) 
 integer, parameter :: iprec2 = selected_int_kind(r4)
 integer, parameter :: iprec3 = selected_int_kind(r5)
 integer, parameter :: iprec4 = selected_int_kind(r6) 
 
 real(rprec1)    :: n1
 real(rprec2)    :: n2
 real(rprec3)    :: n3
 integer(iprec1) :: n4
 integer(iprec2) :: n5
 integer(iprec3) :: n6
 integer(iprec4) :: n7
 character(30) :: form
 
 form = "(a7, i11, i10, i6, i9, i8)"
 write(*, "(a)") "KIND NAME   KIND NUMBER   PRECISION        RANGE "
 write(*, "(a)") "                          min   set     min     set"
 write(*, "(a)") "______________________________________________________"
 write(*, form) "rprec1", kind(n1), p1, precision(n1), r1, range(n1)
 write(*, form) "rprec2", kind(n2), p2, precision(n2), r1, range(n2)
 write(*, form) "rprec3", kind(n3), p2, precision(n3), r2, range(n3)
 write(*,*)
 form = "(a7, i11, i25, i8)"
 write(*, form) "iprec1", kind(n4), r3, range(n4) 
 write(*, form) "iprec2", kind(n5), r4, range(n5) 
 write(*, form) "iprec3", kind(n6), r5, range(n6)
 write(*, form) "iprec4", kind(n7), r6, range(n7)

end program</lang> Output

KIND NAME   KIND NUMBER   PRECISION        RANGE
                          min   set     min     set
______________________________________________________
 rprec1          1         6     6       30      37
 rprec2          2        12    15       30     307
 rprec3          3        12    18     1000    4931
 
 iprec1          1                        2       2
 iprec2          2                        4       4
 iprec3          3                        8       9
 iprec4          4                       16      18

Go

Translation of: Ada

For task interpretation this follows the spirit of the Ada example included by the task author. In it, an enumeration type is defined from enumeration values, then a storage size--smaller than the default--is specified for the type. A similar situation exists within Go. Defining types from values is called duck-typing, and the situation where a type smaller than the default can be specified exists when a variable is duck-typed from a numeric literal. <lang go>package main

import (

   "fmt"
   "unsafe"

)

func main() {

   i := 5   // default type is int
   r := '5' // default type is rune (which is int32)
   f := 5.  // default type is float64
   c := 5i  // default type is complex128
   fmt.Println("i:", unsafe.Sizeof(i), "bytes")
   fmt.Println("r:", unsafe.Sizeof(r), "bytes")
   fmt.Println("f:", unsafe.Sizeof(f), "bytes")
   fmt.Println("c:", unsafe.Sizeof(c), "bytes")
   iMin := int8(5)
   rMin := byte('5')
   fMin := float32(5.)
   cMin := complex64(5i)
   fmt.Println("iMin:", unsafe.Sizeof(iMin), "bytes")
   fmt.Println("rMin:", unsafe.Sizeof(rMin), "bytes")
   fmt.Println("fMin:", unsafe.Sizeof(fMin), "bytes")
   fmt.Println("cMin:", unsafe.Sizeof(cMin), "bytes")

}</lang> Output:

i: 4 bytes
r: 4 bytes
f: 8 bytes
c: 16 bytes
iMin: 1 bytes
rMin: 1 bytes
fMin: 4 bytes
cMin: 8 bytes

Icon and Unicon

Icon and Unicon values are self-descriptive types subject to automatic garbage collection. As a result the opportunities for setting the sizes of the variables are limited.

• strings are always variable in length with some fixed overhead
• csets are a fixed size
• tables and sets are variable in size and start empty
• integers and reals are fixed sizes
• records are a fized size
• co-expressions vary in size based on the environment when they are created
• file, window, and procedure references are all fixed in size
• lists can be specified with a minimum size (see below):

<lang Icon> L := list(10) # 10 element list </lang>

J

<lang J>v=: </lang>

Here, v is specified to have a minimum size. In this case, the minimum size of the content is zero, though the size of the representation is somewhat larger.

Mathematica

Mathematica stores variables in symbols : e.g. variable 'A' containing integer 0 requires 24 bytes under Windows.

Modula-3

<lang modula3>TYPE UByte = BITS 8 FOR [0..255];</lang> Note that this only works for records, arrays, and objects. Also note that the size in bits must be large enough to hold the entire range (in this case, 8 bits is the correct amount for the range 0 to 255) or the compiler will error.

ooRexx

ooRexx variables are all references to object instances, so the variables themselves have no settable or gettable size.

PARI/GP

<lang parigp>default(precision, 1000)</lang> Alternately, in the gp interpreter, <lang parigp>\p 1000</lang>

Pascal

Ordinal and floating point types of FreePascal are listed here: [[1]] and here: [[2]] <lang pascal>var

 a: byte;     // 1 byte
 b: word;     // 2 byte
 c: cardinal; // 4 byte
 d: QWord;    // 8 byte

 x: real;   // 4 byte
 y: double; // 8 byte</lang>

Perl

I suppose you could use vec() or similar to twiddle a single bit. The thing is, as soon as you store this in a variable, the SV (the underlying C implementation of the most simple data type) already takes a couple dozen of bytes.

In Perl, memory is readily and happily traded for expressiveness and ease of use.

PL/I

<lang PL/I> declare i fixed binary (7), /* occupies one byte */

       j fixed binary (15), /* occupies two bytes */
       k fixed binary (31), /* occupies 4 bytes   */
       l fixed binary (63); /* occupies 8 bytes   */

declare d fixed decimal (1), /* occupies 1 byte */

       e fixed decimal (3), /* occupies 2 bytes   */
                            /* an so on ...       */
       f fixed decimal (15); /* occupies 8 bytes. */

declare b(16) bit (1) unaligned; /* occupies 2 bytes */ declare c(16) bit (1) aligned; /* occupies 16 bytes */

declare x float, /* occupies 4 bytes. */

       y float (15),         /* occupies 8 bytes. */
       z float (18);         /* occupies 10 bytes */

</lang>

PicoLisp

In PicoLisp, all variables have the same size (a single cell). But it is possible to create a data structure of a given minimal size with the 'need' function.

Python

For compatibility with the calling conventions of external C functions, the ctypes module has functions that map data types and sizes between Python and C:

ctypes type	C type	Python type
c_char	char	1-character string
c_wchar	wchar_t	1-character unicode string
c_byte	char	int/long
c_ubyte	unsigned char	int/long
c_short	short	int/long
c_ushort	unsigned short	int/long
c_int	int	int/long
c_uint	unsigned int	int/long
c_long	long	int/long
c_ulong	unsigned long	int/long
c_longlong	__int64 or long long	int/long
c_ulonglong	unsigned __int64 or unsigned long long	int/long
c_float	float	float
c_double	double	float
c_longdouble	long double	float
c_char_p	char * (NUL terminated)	string or None
c_wchar_p	wchar_t * (NUL terminated)	unicode or None
c_void_p	void *	int/long or None

REXX

In REXX, there are no minimums for variables holding character literals, so you just simply assign (set) character strings to REXX variables.
Note that REXX stores all the values of variables as characters, and that includes numbers (all kinds), booleans (logical), and labels (including subroutine/function names).
However, to insure that REXX can store numbers with a minimum size (amount of digits), the   NUMERIC DIGITS nnn   instruction can be used.   This will ensure that the number can be stored without resorting to exponential notation   (although exponential notation can be forced via the   FORMAT   BIF.

The default is 9 digits.

There's effectively is no limit for the precision [or length] for REXX numbers (except for memory), but eight million is the practical limit. <lang rexx>numeric digits 100 abc=12345678901111111112222222222333333333344444444445555555555.66</lang>

Tcl

In Tcl, most values are (Unicode) strings. Their size is measured in characters, and the minimum size of a string is of course 0. However, one can arrange, via write traces, that the value of a variable is reformatted to bigger size. Examples, from an interactive tclsh session: <lang Tcl>% proc format_trace {fmt _var el op} {upvar 1 $_var v; set v [format $fmt $v]}

% trace var foo w {format_trace %10s} % puts "/[set foo bar]/" / bar/

% trace var grill w {format_trace %-10s} % puts "/[set grill bar]/" /bar /</lang> ..or limit its size to a certain length: <lang Tcl>% proc range_trace {n _var el op} {upvar 1 $_var v; set v [string range $v 0 [incr n -1]]}

% trace var baz w {range_trace 2} % set baz Frankfurt Fr</lang>

Ursala

There is no way to set the minimum size of natural, integer, or rational numbers, but no need because they all have unlimited precision.

For (mpfr format) arbitrary precision floating point numbers, there are several mechanisms for setting the minimum precision, although not the exact amount of real memory used.

• If it's initialized from a literal constant, the compiler infers the intended precision from the number of digits in the constant (or 160 bits, whichever is greater).
• The library function mpfr..grow(x,n) returns a copy of x with its precision increased by n bits (padded with zeros).
• The library function mpfr..shrink(x,n) returns a copy of x with its precision reduced by n bits, or to MPFR_PREC_MIN, whichever is greater.
• Library functions such as mpfr..pi and mpfr..const_catalan take a natural number specifying the precision as an argument and return a constant with at least that precision.
• If two numbers of unequal precision are combined using any binary operation from the mpfr library, the result is computed and allocated using the greater precision of the two.

The last feature eliminates the need for explicitly setting the precision of numbers having exact representations, albeit contrary to the convention in physical sciences. <lang Ursala>p = mpfr..pi 200 # 200 bits of precision

x = mpfr..grow(1.0E+0,1000) # 160 default precision, grown to 1160

y = mpfr..shrink(1.0+0,40) # 160 default shrunk to 120

z = mpfr..add(p,y) # inherits 200 bits of precision

a = # 180 bits (not the default 160) because of more digits in the constant

1.00000000000000000000000000000000000000000000000000000E0</lang>

XPL0

<lang XPL0>include c:\cxpl\codes; \intrinsic 'code' declarations string 0; \use zero-terminated strings char S,

    A(1),              \sets up an array containing one byte
    B(0);              \sets up an array containing no bytes

int I; [S:= ""; \a zero-length (null) string A:= Reserve(1); \sets up a 1-byte array at runtime B:= Reserve(0); \sets up a 0-byte array at runtime I:= I ! 1<<3; \stores a single 1 bit into an integer I:= I & ~(1<<29); \stores a 0 bit into bit 29 of the integer IntOut(0, I>>3 & 1); \displays value of bit 3 ]</lang>

Other than arrays and strings, variables are a fixed size. Integers are four bytes and reals are eight bytes.

ZX Spectrum Basic

<lang basic>10 DIM a$(10): REM This array will be 10 characters long 20 DIM b(10): REM this will hold a set of numbers. The fixed number of bytes per number is implementation specific 30 LET c=5: REM this is a single numerical value of fixed size</lang>