Difference between revisions of "Real"

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'''real''' is a [[Standard type|standard type]] of the [[Pascal]] Programming language.  It is used to define a floating point number which may contain a decimal point and possibly an exponent, as opposed to a [[Integer]] data type, used to define a whole number.
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{{Real}}
  
The size may vary from  6 bytes, 48 bits (you may rapresent numbers from 10^-32 to 10^32) to 8 [[bytes]] 68 bits (10^-300 to 10^300).
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<syntaxhighlight lang="pascal" inline>real</syntaxhighlight> is a [[Standard type|standard type]] of the [[Pascal]] programming language.
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== usage ==
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Floating-point literals can be assigned to <syntaxhighlight lang="pascal" inline>real</syntaxhighlight> variables.
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<syntaxhighlight lang="pascal" line>
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program realDemo(input, output, stderr);
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var
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r: real;
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begin
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r := 0.; // r becomes zero
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writeLn(r, ' ', r:8:4);
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r := 1e2; // r becomes 1*(10^2) [a hundred]
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writeLn(r, ' ', r:8:4);
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r := r / r; // r becomes one
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writeLn(r, ' ', r:8:4);
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end.
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</syntaxhighlight>
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<syntaxhighlight lang="pascal" inline>real</syntaxhighlight>, like all floating-point types, supports [[Slash#division|<syntaxhighlight lang="pascal" inline>/</syntaxhighlight> division operator]], while integer types support <syntaxhighlight lang="pascal" inline>div</syntaxhighlight>-operator.
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== internal representation ==
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The internal representation of the type <syntaxhighlight lang="pascal" inline>real</syntaxhighlight> (i.e. number of bytes and byte ordering) and the resulting range and precision are platform dependent.
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Quote from the “FreePascal Programmer's Manual” (Chapter 8.2.5 [https://www.freepascal.org/docs-html/prog/progsu158.html Floating point types]):
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<blockquote>
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Contrary to Turbo Pascal, where the <syntaxhighlight lang="pascal" inline>real</syntaxhighlight> type had a special internal format, under Free Pascal the <syntaxhighlight lang="pascal" inline>real</syntaxhighlight> type simply maps to one of the other real types.
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It maps to the [[Double|<syntaxhighlight lang="pascal" inline>double</syntaxhighlight> type]] on processors which support floating point operations, while it maps to the [[Single|<syntaxhighlight lang="pascal" inline>single</syntaxhighlight> type]] on processors which do not support floating point operations in hardware.
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</blockquote>
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== alternatives ==
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Instead of specifying <syntaxhighlight lang="pascal" inline>real</syntaxhighlight> in your code, write {{Doc|package=RTL|unit=system|identifier=valreal|text=<syntaxhighlight lang="pascal" inline>ValReal</syntaxhighlight>}}, a type alias defined by the [[System unit]].
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It automatically maps to the largest available floating point type available: <syntaxhighlight lang="pascal" inline>single</syntaxhighlight>, <syntaxhighlight lang="pascal" inline>double</syntaxhighlight> or <syntaxhighlight lang="pascal" inline>extended</syntaxhighlight>.
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{{Data types}}

Latest revision as of 17:36, 6 March 2022

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real is a standard type of the Pascal programming language.

usage

Floating-point literals can be assigned to real variables.

 1program realDemo(input, output, stderr);
 2
 3var
 4	r: real;
 5
 6begin
 7	r := 0.; // r becomes zero
 8	writeLn(r, ' ', r:8:4);
 9	
10	r := 1e2; // r becomes 1*(10^2) [a hundred]
11	writeLn(r, ' ', r:8:4);
12	
13	r := r / r; // r becomes one
14	writeLn(r, ' ', r:8:4);
15end.

real, like all floating-point types, supports / division operator, while integer types support div-operator.

internal representation

The internal representation of the type real (i.e. number of bytes and byte ordering) and the resulting range and precision are platform dependent.

Quote from the “FreePascal Programmer's Manual” (Chapter 8.2.5 Floating point types):

Contrary to Turbo Pascal, where the real type had a special internal format, under Free Pascal the real type simply maps to one of the other real types. It maps to the double type on processors which support floating point operations, while it maps to the single type on processors which do not support floating point operations in hardware.

alternatives

Instead of specifying real in your code, write ValReal, a type alias defined by the System unit. It automatically maps to the largest available floating point type available: single, double or extended.


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