78 lines
3.1 KiB
HTML
78 lines
3.1 KiB
HTML
<html>
|
|
|
|
<head>
|
|
<object type="application/x-oleobject" classid="clsid:1e2a7bd0-dab9-11d0-b93a-00c04fc99f9e">
|
|
<param name="Keyword" value="var">
|
|
</object>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=windows-1251">
|
|
<title></title>
|
|
<link rel="StyleSheet" href="../../default.css">
|
|
</head>
|
|
|
|
<body>
|
|
<H1>Îïèñàíèå ïåðåìåííûõ</H1>
|
|
<p class="pabcmain">Ïåðåìåííûå ìîãóò áûòü îïèñàíû â ðàçäåëå îïèñàíèé, à òàêæå
|
|
íåïîñðåäñòâåííî âíóòðè ëþáîãî áëîêà <b><code>begin</code></b>/<b><code>end</code></b>.</p>
|
|
<p class="pabcmain">Ðàçäåë îïèñàíèÿ ïåðåìåííûõ íà÷èíàåòñÿ
|
|
ñ êëþ÷åâîãî ñëîâà <b><code>var</code></b>,
|
|
ïîñëå êîòîðîãî ñëåäóþò ýëåìåíòû îïèñàíèÿ âèäà</p>
|
|
<blockquote>
|
|
<code class="codeit">ñïèñîê èìåí</code><code>:</code><code class="codeit">
|
|
òèï</code><code>;</code></blockquote>
|
|
<p class="pabcmain">èëè</p>
|
|
<blockquote>
|
|
<code class="codeit">èìÿ</code><code>:</code><code class="codeit">
|
|
òèï </code><code>:=</code><code class="codeit"> âûðàæåíèå</code><code>;</code>
|
|
</blockquote>
|
|
<p class="pabcmain">èëè</p>
|
|
<blockquote>
|
|
<code class="codeit">èìÿ</code><code>:</code><code class="codeit">
|
|
òèï </code><code>=</code><code class="codeit"> âûðàæåíèå</code><code>;</code>
|
|
<code>// äëÿ ñîâìåñòèìîñòè ñ Delphi </code>
|
|
</blockquote>
|
|
<p class="pabcmain">èëè</p>
|
|
<blockquote>
|
|
<code class="codeit">èìÿ </code><code>:=</code><code class="codeit">
|
|
âûðàæåíèå</code><code>;</code>
|
|
</blockquote>
|
|
<p class="pabcmain">Èìåíà â ñïèñêå ïåðå÷èñëÿþòñÿ ÷åðåç çàïÿòóþ. Íàïðèìåð:</p>
|
|
<blockquote>
|
|
<p><code><b>var<br>
|
|
</b>a,b,c: integer;<br>
|
|
d: real := 3.7;<br>
|
|
s := 'PascalABC forever';<br>
|
|
al := new List<integer>;</code><br>
|
|
<code> p1 := 1;</code></p>
|
|
</blockquote>
|
|
<p class="pabcmain"> ïîñëåäíèõ òðåõ ñëó÷àÿõ òèï ïåðåìåííîé àâòîìàòè÷åñêè îïðåäåëÿåòñÿ
|
|
ïî òèïó ïðàâîé ÷àñòè.</p>
|
|
<p>Ïåðåìåííûå ìîãóò îïèñûâàòüñÿ íåïîñðåäñòâåííî âíóòðè
|
|
<a href="../Operators/beginend.html">áëîêà</a>. Òàêèå îïèñàíèÿ íàçûâàþòñÿ
|
|
âíóòðèáëî÷íûìè è ïðåäñòàâëÿþò ñîáîé <a href="../Operators/var_statement.html">
|
|
îïåðàòîð îïèñàíèÿ ïåðåìåííîé</a>.</p>
|
|
<p>Êðîìå òîãî, ïåðåìåííûå-ïàðàìåòðû öèêëà ìîãóò îïèñûâàòüñÿ â çàãîëîâêå
|
|
îïåðàòîðîâ <code><b><a href="../Operators/for.html">for</a></b></code> è <code><b>
|
|
<a href="../Operators/foreach.html">foreach</a></b></code>.</p>
|
|
<p>Ãëîáàëüíûå ïåðåìåííûå èíèöèàëèçèðóþòñÿ íóëåâûìè çíà÷åíèÿìè. Äëÿ ëîêàëüíûõ
|
|
ïåðåìåííûõ ýòî íå ãàðàíòèðóåòñÿ - èõ íàäî èíèöèàëèçèðîâàòü ÿâíî. </p>
|
|
<h2>Ñîâìåùåíèå îïèñàíèÿ ïåðåìåííûõ è êîðòåæíîãî ïðèñâàèâàíèÿ</h2>
|
|
<p><a href="../Types/tuples.html">Êîðòåæíîå ïðèñâàèâàíèå</a> (ðàñïàêîâêó êîðòåæà
|
|
â ïåðåìåííûå) ìîæíî ñîâìåùàòü ñ îïèñàíèåì ïåðåìåííûõ:</p>
|
|
|
|
<blockquote>
|
|
<code>var t := (1,2);<br>(<strong>var </strong>a,<strong> var </strong>b) := (1,2);</code></blockquote>
|
|
<p>èëè</p>
|
|
|
|
<blockquote>
|
|
<code><strong>var</strong> (a,b) := (1,2);</code></blockquote>
|
|
<p>Ðàñïàêîâêà êîðòåæà â ïåðåìåííûå ÷àñòî èñïîëüçóåòñÿ ïðè âîçâðàùåíèè ôóíêöèåé
|
|
êîðòåæà:</p>
|
|
<blockquote>
|
|
<code><strong>function</strong> SP(a,b: real) := (a*b,2*(a+b)); </code> <br>
|
|
...<br>
|
|
<code><strong>var</strong> (S,P) := SP(2,3); </code>
|
|
</blockquote>
|
|
</body>
|
|
|
|
</html>
|