diff options
Diffstat (limited to 'doc/eval.n')
| -rw-r--r-- | doc/eval.n | 25 |
1 files changed, 16 insertions, 9 deletions
@@ -5,10 +5,8 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: eval.n,v 1.11 2008/06/29 22:28:24 dkf Exp $ -'\" -.so man.macros .TH eval n "" Tcl "Tcl Built-In Commands" +.so man.macros .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME @@ -27,11 +25,13 @@ evaluation (or any error generated by it). Note that the \fBlist\fR command quotes sequences of words in such a way that they are not further expanded by the \fBeval\fR command. .SH EXAMPLES +.PP Often, it is useful to store a fragment of a script in a variable and execute it later on with extra values appended. This technique is used in a number of places throughout the Tcl core (e.g. in \fBfcopy\fR, \fBlsort\fR and \fBtrace\fR command callbacks). This example shows how to do this using core Tcl commands: +.PP .CS set script { puts "logging now" @@ -57,21 +57,28 @@ easier to make robust in practice. The following procedure acts in a way that is analogous to the \fBlappend\fR command, except it inserts the argument values at the start of the list in the variable: +.PP .CS proc lprepend {varName args} { - upvar 1 $varName var - # Ensure that the variable exists and contains a list - lappend var - # Now we insert all the arguments in one go - set var [\fBeval\fR [list linsert $var 0] $args] + upvar 1 $varName var + # Ensure that the variable exists and contains a list + lappend var + # Now we insert all the arguments in one go + set var [\fBeval\fR [list linsert $var 0] $args] } .CE +.PP However, the last line would now normally be written without \fBeval\fR, like this: +.PP .CS set var [linsert $var 0 {*}$args] .CE .SH "SEE ALSO" -catch(n), concat(n), error(n), interp(n), list(n), namespace(n), subst(n), tclvars(n), uplevel(n) +catch(n), concat(n), error(n), errorCode(n), errorInfo(n), interp(n), list(n), +namespace(n), subst(n), uplevel(n) .SH KEYWORDS concatenate, evaluate, script +'\" Local Variables: +'\" mode: nroff +'\" End: |