Difference between revisions of "Real"

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(Real is not a rational number (see: https://en.wikipedia.org/wiki/Rational_number))
(→‎alternatives: del dead svn link)
 
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{{Real}}
 
{{Real}}
  
<syntaxhighlight lang="pascal" enclose="none">real</syntaxhighlight> is a [[Standard type|standard type]] of the [[Pascal]] programming language.
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<syntaxhighlight lang="pascal" inline>real</syntaxhighlight> is a [[Standard type|standard type]] of the [[Pascal]] programming language.
  
 
== usage ==
 
== usage ==
Floating-point literals can be assigned to <syntaxhighlight lang="pascal" enclose="none">real</syntaxhighlight> variables.
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Floating-point literals can be assigned to <syntaxhighlight lang="pascal" inline>real</syntaxhighlight> variables.
 
<syntaxhighlight lang="pascal" line>
 
<syntaxhighlight lang="pascal" line>
 
program realDemo(input, output, stderr);
 
program realDemo(input, output, stderr);
Line 22: Line 22:
 
end.
 
end.
 
</syntaxhighlight>
 
</syntaxhighlight>
Note, that the result of the [[Slash#division|<syntaxhighlight lang="pascal" enclose="none">/</syntaxhighlight>-division]] can be assigned.
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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.
  
 
== internal representation ==
 
== internal representation ==
The internal representation of the type <syntaxhighlight lang="pascal" enclose="none">real</syntaxhighlight> (i.e. number of bytes and byte ordering) and the resulting range and precision are platform dependent.
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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.
  
Quote from the “FreePascal Programmer's Manual” (Chapter 8.2.5 [https://www.freepascal.org/docs-html/prog/progsu159.html Floating point types]):
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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]):
 
<blockquote>
 
<blockquote>
Contrary to Turbo Pascal, where the <syntaxhighlight lang="pascal" enclose="none">real</syntaxhighlight> type had a special internal format, under Free Pascal the <syntaxhighlight lang="pascal" enclose="none">real</syntaxhighlight> type simply maps to one of the other real types.
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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.
It maps to the [[Double|<syntaxhighlight lang="pascal" enclose="none">double</syntaxhighlight> type]] on processors which support floating point operations, while it maps to the [[Single|<syntaxhighlight lang="pascal" enclose="none">single</syntaxhighlight> type]] on processors which do not support floating point operations in hardware.
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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.
 
</blockquote>
 
</blockquote>
  
 
== alternatives ==
 
== alternatives ==
Instead of specifying <syntaxhighlight lang="pascal" enclose="none">real</syntaxhighlight> in your code, write {{Doc|package=RTL|unit=system|identfier=valreal|text=<syntaxhighlight lang="pascal" enclose="none">valReal</syntaxhighlight>}}, a type alias [https://svn.freepascal.org/cgi-bin/viewvc.cgi/tags/release_3_0_4/rtl/inc/systemh.inc?revision=37113&view=markup#l105 defined by] the [[System unit|system unit]].
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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]].
It automatically maps to the largest available floating point type available.
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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>.
  
 
{{Data types}}
 
{{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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