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<!DOCTYPE html>
<html>
<head>
<title>循环结构:循环语句</title>
<meta charset="utf-8">
<link rel="stylesheet" href="style.css">
</head>
<body>
<header>
<h1>七、循环结构:循环语句</h1>
</header>
<section>
<a href="index.html" class="home-link">返回首页</a>
<h2>次数未知</h2>
<h3>当型循环</h3>
<p>
1.使用do while语句实现当型循环,当while后括号内为".true."时,重复执行循环体内的语句,如下:
<div class="code-container">
<span class="keywordblue">integer</span>::n=1
<span class="keywordred">do while</span> (n<=50)
<span class="keywordred">print</span>*, <span class="keywordbrown">'now, n='</span>,n
<span class="keywordred">print</span>*, <span class="keywordbrown">'let us continue.'</span>
n=n+1
<span class="keywordred">end do</span>
</div><br />
2.也可以采用有标号的格式,如下:
<div class="code-container">
<span class="keywordblue">integer</span>::n=1
<span class="keywordred">do 10 while</span> (n<=50)
<span class="keywordred">print</span>*, <span class="keywordbrown">'now, n='</span>,n
<span class="keywordred">print</span>*, <span class="keywordbrown">'let us continue.'</span>
n=n+1
10 <span class="keywordred">continue</span>
<span class="keywordred">end</span>
</div><br />
3.还可以借助if和go to 语句实现:
<div class="code-container">
<span class="keywordblue">integer</span>::n=1
a <span class="keywordred">if</span> (n<=50) then
<span class="keywordred">print</span>*, <span class="keywordbrown">'now, n='</span>,n
<span class="keywordred">print</span>*, <span class="keywordbrown">'let us continue.'</span>
n=n+1
<span class="keywordred">go to</span> a
<span class="keywordred">end if</span>
</div><br />
<h3>直到型循环</h3>
1.使用go to 语句实现:
<div class="code-container">
<span class="keywordblue">integer</span>::n=1
a <span class="keywordred">print</span>*, <span class="keywordbrown">'now, n='</span>,n
<span class="keywordred">print</span>*, <span class="keywordbrown">'let us continue.'</span>
n=n+1
<span class="keywordred">if</span>(n<=50)<span class="keywordred">go to</span> a
</div><br />
2.使用do和exit语句实现
<div class="code-container">
<span class="keywordblue">integer</span>::n=1
<span class="keywordred">do</span>
<span class="keywordred">print</span>*, <span class="keywordbrown">'now, n='</span>,n
<span class="keywordred">print</span>*, <span class="keywordbrown">'let us continue.'</span>
n=n+1
<span class="keywordred">if</span> (n<=50) exit
<span class="keywordred">end do</span>
</div><br />
<h2>次数已知</h2>
可以使用do 加上循环变量来进行指定次数的循环,如下:
<div class="code-container">
<span class="keywordred">do</span> i = 1,5,1
<span class="keywordred">print</span>*, <span class="keywordbrown">'now, n='</span>,n
<span class="keywordred">print</span>*, <span class="keywordbrown">'let us continue.'</span>
<span class="keywordred">end do</span>
</div><br />
其中do语句后面的 i=1,5,1 表示设定循环变量i的初值为1,终值为5,步长为1。<br />
也可以使用如下带标号的格式:
<div class="code-container">
<span class="keywordred">do</span> 10 i = 1,5,1
<span class="keywordred">print</span>*, <span class="keywordbrown">'now, n='</span>,n
<span class="keywordred">print</span>*, <span class="keywordbrown">'let us continue.'</span>
10 <span class="keywordred">continue</span>
</div><br />
</p>
<br />
<br />
<br />
<br />
<br />
</section>
<footer>
<p>© 韦境量 本项目的<a href="https://github.com/jingliangwei/a-crash-course-for-Fortran">github</a>链接</p>
</footer>
</body>
</html>