*: what changed
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Title: *
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| 1 | + | * | |
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| 3 | + | ## standard Pascal | |
| 4 | + | ||
| 5 | + | The symbol `*`, pronounced “asterisk”, is used in [[Pascal]] to | |
| 6 | + | ||
| 7 | + | - indicate multiplication of numbers, or | |
| 8 | + | - form the intersection of [[Set|sets]]. | |
| 9 | + | ||
| 10 | + | ``` pascal | |
| 11 | + | program asteriskDemo(input, output, stderr); | |
| 12 | + | ||
| 13 | + | type | |
| 14 | + | day = (monday, tuesday, wednesday, | |
| 15 | + | thursday, friday, saturday, sunday); | |
| 16 | + | ||
| 17 | + | var | |
| 18 | + | i: longint; | |
| 19 | + | n: real; | |
| 20 | + | m: set of day; | |
| 21 | + | ||
| 22 | + | begin | |
| 23 | + | // multiplication operator | |
| 24 | + | i := 6 * 7; // i becomes 42 | |
| 25 | + | n := 6.0 * 7.0; // n becomes 42.0 | |
| 26 | + | ||
| 27 | + | // intersection operator | |
| 28 | + | m := [saturday, sunday] * [sunday, monday]; | |
| 29 | + | // m is now {sunday} | |
| 30 | + | end. | |
| 31 | + | ``` | |
| 32 | + | ||
| 33 | + | ## exponentiation | |
| 34 | + | ||
| 35 | + | Furthermore, in [[FPC]] the exponentiation operator consisting of two consecutive asterisks `**` exists. However, it is only [defined for variants](https://www.freepascal.org/docs-html/rtl/system/.op-power-variant-ariant-ariant.html) by the standard system unit, which requires a variant manager being installed. In order to actually use it with integers, one can [[Operator overloading|define]] it on their own: | |
| 36 | + | ||
| 37 | + | ``` pascal | |
| 38 | + | program exponentiation(input, output, stdErr); | |
| 39 | + | ||
| 40 | + | // make operator overloading available | |
| 41 | + | {$mode objFPC} | |
| 42 | + | ||
| 43 | + | operator ** (const base: integer; const exponent: integer): integer; | |
| 44 | + | begin | |
| 45 | + | if base <> 0 then | |
| 46 | + | begin | |
| 47 | + | result := trunc(exp(ln(base) * exponent)); | |
| 48 | + | end; | |
| 49 | + | end; | |
| 50 | + | ||
| 51 | + | begin | |
| 52 | + | writeLn(2 ** 10); // will print 1024 | |
| 53 | + | end. | |
| 54 | + | ``` | |
| 55 | + | ||
| 56 | + | For readily available overloads, the [`math`](https://www.freepascal.org/docs-html/rtl/math/index.html) and [`matrix` unit](https://www.freepascal.org/docs-html/rtl/matrix/index.html) can be [[Uses|included]]. | |
| 57 | + | ||
| 58 | + | ## other appearances | |
| 59 | + | ||
| 60 | + | In Pascal's years of childhood computer systems did not necessarily knew the [[Comments|comment]] delimiting characters opening and closing curly brace `{ }`. To make block comments available on such systems an alternative syntax, the bigramms `(*` and `*)` are allowed, too, but they can't be interchanged willynilly: `(*` *has* to match a `*)`, and can *not* match a `}` even though it is closing a block comment, too. | |
| 61 | + | ||
| 62 | + | Also, if C like operators were allowed by the compiler directive [[sCoperator|{$COperator on}]], the short syntax for `i := i * n` reads `i *= n`. But by doing so, you leave the domain of Pascal. Your code technically, mathematically speaking becomes wrong. | |
| 63 | + | ||
| 64 | + | In [[ASCII]], the character code decimal `42` (or [[Hexadecimal|hexadecimal]] `2A`) is defined to be `*`. | |
| 65 | + | ||
| 66 | + | --- | |
| 67 | + | *From the Free Pascal wiki, page "*", as it stood on 2022-11-27 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](/wiki-contact).* | |
| 68 | + | Category: Code |