Plus

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+

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The symbol + (pronounced “plus”) is used to:

• explicitly indicate the positive sign of a number,
• add two numbers resulting to a number,
• form a union of sets,
• (FPC) concatenate two strings (or characters; except pchar).
• if {$modeSwitch arrayOperators+} (default in {$mode Delphi}), concatenate arrays (since FPC 3.2.0)
• enable a feature in a {$modeSwitch}

program plusDemo(input, output, stderr);

var
    x: longint;
    g: set of (foo, bar);
    m: string;
begin
    // unary operator: positive sign
    x := +7;                    // x becomes positive 7
    x := +$100;                 // x becomes 256
                                // (dollar sign denotes hexadecimal base)
    
    // addition
    x := 7 + 7;                 // x becomes 14
    x := 7 + 7 + 7 + 7 + 7 + 7; // x becomes 42
    
    // union of sets
    g := [foo] + [bar];         // g becomes [foo, bar]
    
    // concatenation of strings and/or characters (FPC/Delphi extension)
    m := 'Hello ' + 'world!';   // m becomes 'Hello world!'
end.

The plus sign is also a unary operator. One can write such stupid expressions as ++++++++++++++42 which will evaluate to positive 42.

In ASCII, the character code decimal 43 (or hexadecimal 2B) is defined to be + (plus sign).

see also

• system.add
• system.concat returns concatenation of strings
• strings.strcat returns concatenation of pchar strings

From the Free Pascal wiki, page "Plus", as it stood on 2019-10-16 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.