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author | rjohnson <rjohnson> | 1998-03-26 14:45:59 (GMT) |
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committer | rjohnson <rjohnson> | 1998-03-26 14:45:59 (GMT) |
commit | 2b5738da524e944cda39e24c0a87b745a43bd8c3 (patch) | |
tree | 6e8c9473978f6dab66c601e911721a7bd9d70b1b /doc/for.n | |
parent | c6a259aeeca4814a97cf6694814c63e74e4e18fa (diff) | |
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diff --git a/doc/for.n b/doc/for.n new file mode 100644 index 0000000..3680cf4 --- /dev/null +++ b/doc/for.n @@ -0,0 +1,60 @@ +'\" +'\" Copyright (c) 1993 The Regents of the University of California. +'\" Copyright (c) 1994-1997 Sun Microsystems, Inc. +'\" +'\" See the file "license.terms" for information on usage and redistribution +'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. +'\" +'\" SCCS: @(#) for.n 1.6 97/04/08 17:13:49 +'\" +.so man.macros +.TH for n "" Tcl "Tcl Built-In Commands" +.BS +'\" Note: do not modify the .SH NAME line immediately below! +.SH NAME +for \- ``For'' loop +.SH SYNOPSIS +\fBfor \fIstart test next body\fR +.BE + +.SH DESCRIPTION +.PP +\fBFor\fR is a looping command, similar in structure to the C +\fBfor\fR statement. The \fIstart\fR, \fInext\fR, and +\fIbody\fR arguments must be Tcl command strings, and \fItest\fR +is an expression string. +The \fBfor\fR command first invokes the Tcl interpreter to +execute \fIstart\fR. Then it repeatedly evaluates \fItest\fR as +an expression; if the result is non-zero it invokes the Tcl +interpreter on \fIbody\fR, then invokes the Tcl interpreter on \fInext\fR, +then repeats the loop. The command terminates when \fItest\fR evaluates +to 0. If a \fBcontinue\fR command is invoked within \fIbody\fR then +any remaining commands in the current execution of \fIbody\fR are skipped; +processing continues by invoking the Tcl interpreter on \fInext\fR, then +evaluating \fItest\fR, and so on. If a \fBbreak\fR command is invoked +within \fIbody\fR +or \fInext\fR, +then the \fBfor\fR command will +return immediately. +The operation of \fBbreak\fR and \fBcontinue\fR are similar to the +corresponding statements in C. +\fBFor\fR returns an empty string. +.PP +Note: \fItest\fR should almost always be enclosed in braces. If not, +variable substitutions will be made before the \fBfor\fR +command starts executing, which means that variable changes +made by the loop body will not be considered in the expression. +This is likely to result in an infinite loop. If \fItest\fR is +enclosed in braces, variable substitutions are delayed until the +expression is evaluated (before +each loop iteration), so changes in the variables will be visible. +For an example, try the following script with and without the braces +around \fB$x<10\fR: +.CS +for {set x 0} {$x<10} {incr x} { + puts "x is $x" +} +.CE + +.SH KEYWORDS +for, iteration, looping |