src/mann/for.n

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   8 '\" RCS: @(#) $Id: for.n,v 1.2 2003/11/24 05:09:59 bbbush Exp $
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  10 '\" The definitions below are for supplemental macros used in Tcl/Tk
  11 '\" manual entries.
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  13 '\" .AP type name in/out ?indent?
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  62 '\" .OP cmdName dbName dbClass
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  64 '\"     option's name as specified in the class command, dbName gives
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 206 '\"     # SO - start of list of standard options
 207 .de SO
 208 .SH "STANDARD OPTIONS"
 209 .LP
 210 .nf
 211 .ta 5.5c 11c
 212 .ft B
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 215 .de SE
 216 .fi
 217 .ft R
 218 .LP
 219 See the \\fBoptions\\fR manual entry for details on the standard options.
 220 ..
 221 '\"     # OP - start of full description for a single option
 222 .de OP
 223 .LP
 224 .nf
 225 .ta 4c
 226 Command-Line Name:      \\fB\\$1\\fR
 227 Database Name:  \\fB\\$2\\fR
 228 Database Class: \\fB\\$3\\fR
 229 .fi
 230 .IP
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 243 .de UL
 244 \\$1\l'|0\(ul'\\$2
 245 ..
 246 .TH for n "" Tcl "Tcl Built-In Commands"
 247 .BS
 248 '\" Note:  do not modify the .SH NAME line immediately below!
 249 .SH NAME
 250 for \- ``For'' 循环
 251 .SH "总览 SYNOPSIS"
 252 \fBfor \fIstart test next body\fR
 253 .BE
 254
 255 .SH "描述 DESCRIPTION"
 256 .PP
 257 \fBFor\fR  是一个循环命令，在结构上类似与 C 语言的 \fBfor\fR语句。\fIstart\fR、\fInext\fR、和\fIbody\fR  参数必须是 Tcl 命令串，而 \fItest\fR 是一个表达式串。\fBfor\fR  命令首先调用 Tcl 解释器来执行 \fIstart\fR。接着它重复的把 \fItest\fR作为一个表达式来求值；如果结果是非零则它在 \fIbody \fR上调用 Tcl 解释器，接着在 \fInext \fR上调用 Tcl 解释器，接着重复这个循环。在 \fItest\fR  被求值为 0 的时候命令终止。如果\fIbody\fR  中调用了 \fBcontinue\fR  命令则在 \fIbody\fR  的当前执行中的所有剩余的命令都被跳过；处理继续，在 \fInext \fR上调用 Tcl 解释器，接着对 \fItest \fR求值。 等等. 如果在 \fIbody\fR 或 \fInext \fR中调用 \fBbreak\fR  命令，则 \fBfor\fR  命令将立即返回。\fBbreak\fR  和 \fBcontinue\fR  命令的操作类似于在 C 语言中相应的语句。\fBFor\fR  返回一个空串。
 258 .PP
 259 注意: \fItest\fR 应当总是在花括号中包围着。如果不是这样，在 \fBfor\fR  命令开始之前就作了变量替换，这意味着在循环体中做的变量变更在表达式中将不被考虑。将导致一个无限循环。如果 \fItest\fR  被包围在花括号中，变量替换将延迟，直到表达式求值(在每次循环重复之前)，所以变量的变更将是可见的。例如，尝试在 \fB$x<10\fR 周围有和没有一对花括号的下列脚本:
 260 .CS
 261 for {set x 0} {$x<10} {incr x} {
 262         puts "x is $x"
 263 }
 264 .CE
 265
 266 .SH "参见 SEE ALSO"
 267 break, continue, foreach, while
 268
 269 .SH "关键字 KEYWORDS"
 270 for, iteration, looping
 271
 272 .SH "[中文版维护人]"
 273 .B 寒蝉退士
 274 .SH "[中文版最新更新]"
 275 .B 2001/08/05
 276 .SH "《中国 Linux 论坛 man 手册页翻译计划》:"
 277 .BI http://cmpp.linuxforum.net