Difference between revisions of "Real"
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{{Real}} | {{Real}} | ||
| − | <syntaxhighlight lang="pascal" | + | <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" | + | 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" | + | Note, that the result of the [[Slash#division|<syntaxhighlight lang="pascal" inline>/</syntaxhighlight>-division]] can be assigned. |
== internal representation == | == internal representation == | ||
| − | The internal representation of the type <syntaxhighlight lang="pascal" | + | 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]): | Quote from the “FreePascal Programmer's Manual” (Chapter 8.2.5 [https://www.freepascal.org/docs-html/prog/progsu159.html Floating point types]): | ||
<blockquote> | <blockquote> | ||
| − | Contrary to Turbo Pascal, where the <syntaxhighlight lang="pascal" | + | 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" | + | 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" | + | 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 [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]]. |
It automatically maps to the largest available floating point type available. | It automatically maps to the largest available floating point type available. | ||
{{Data types}} | {{Data types}} | ||
Revision as of 15:23, 17 February 2021
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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.
Note, that the result of the /-division can be assigned.
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
realtype had a special internal format, under Free Pascal therealtype simply maps to one of the other real types. It maps to thedoubletype on processors which support floating point operations, while it maps to thesingletype 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.
| simple data types |
|
|---|---|
| complex data types |
