diff options
Diffstat (limited to 'doc/upvar.n')
| -rw-r--r-- | doc/upvar.n | 25 |
1 files changed, 15 insertions, 10 deletions
diff --git a/doc/upvar.n b/doc/upvar.n index a255485..8985d24 100644 --- a/doc/upvar.n +++ b/doc/upvar.n @@ -43,16 +43,18 @@ The \fBupvar\fR command simplifies the implementation of call-by-name procedure calling and also makes it easier to build new control constructs as Tcl procedures. For example, consider the following procedure: +.PP .CS proc \fIadd2\fR name { - \fBupvar\fR $name x - set x [expr {$x + 2}] + \fBupvar\fR $name x + set x [expr {$x + 2}] } .CE +.PP If \fIadd2\fR is invoked with an argument giving the name of a variable, it adds two to the value of that variable. Although \fIadd2\fR could have been implemented using \fBuplevel\fR -instead of \fBupvar\fR, \fBupvar\fR makes it simpler for \fBadd2\fR +instead of \fBupvar\fR, \fBupvar\fR makes it simpler for \fIadd2\fR to access the variable in the caller's procedure frame. .PP \fBnamespace eval\fR is another way (besides procedure calls) @@ -60,7 +62,7 @@ that the Tcl naming context can change. It adds a call frame to the stack to represent the namespace context. This means each \fBnamespace eval\fR command counts as another call level for \fBuplevel\fR and \fBupvar\fR commands. -For example, \fBinfo level 1\fR will return a list +For example, \fBinfo level\fR \fB1\fR will return a list describing a command that is either the outermost procedure call or the outermost \fBnamespace eval\fR command. Also, \fBuplevel #0\fR evaluates a script @@ -83,13 +85,14 @@ will be .QW "\fIlocalVar\fR" rather than .QW "\fIoriginalVar\fR" : +.PP .CS proc \fItraceproc\fR { name index op } { - puts $name + puts $name } proc \fIsetByUpvar\fR { name value } { - \fBupvar\fR $name localVar - set localVar $value + \fBupvar\fR $name localVar + set localVar $value } set originalVar 1 trace variable originalVar w \fItraceproc\fR @@ -104,15 +107,17 @@ made to \fImyVar\fR will not be passed to subprocesses correctly. .SH EXAMPLE A \fBdecr\fR command that works like \fBincr\fR except it subtracts the value from the variable instead of adding it: +.PP .CS proc decr {varName {decrement 1}} { \fBupvar\fR 1 $varName var incr var [expr {-$decrement}] } .CE - .SH "SEE ALSO" global(n), namespace(n), uplevel(n), variable(n) - .SH KEYWORDS -context, frame, global, level, namespace, procedure, variable +context, frame, global, level, namespace, procedure, upvar, variable +.\" Local Variables: +.\" mode: nroff +.\" End: |