diff options
Diffstat (limited to 'doc/proc.n')
| -rw-r--r-- | doc/proc.n | 63 |
1 files changed, 45 insertions, 18 deletions
@@ -4,7 +4,7 @@ '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. -'\" +'\" .TH proc n "" Tcl "Tcl Built-In Commands" .so man.macros .BS @@ -14,7 +14,6 @@ proc \- Create a Tcl procedure .SH SYNOPSIS \fBproc \fIname args body\fR .BE - .SH DESCRIPTION .PP The \fBproc\fR command creates a new Tcl procedure named @@ -33,10 +32,11 @@ elements specifies one argument. Each argument specifier is also a list with either one or two fields. If there is only a single field in the specifier then it is the name of the argument; if there are two fields, then -the first is the argument name and the second is its default value. +the first is the argument name and the second is its default value. Arguments with default values that are followed by non-defaulted -arguments become required arguments. In 8.6 this will be considered an -error. +arguments become required arguments; enough actual arguments must be +supplied to allow all arguments up to and including the last required +formal argument. .PP When \fIname\fR is invoked a local variable will be created for each of the formal arguments to the procedure; its @@ -47,14 +47,17 @@ Arguments with default values need not be specified in a procedure invocation. However, there must be enough actual arguments for all the formal arguments that do not have defaults, and there must not be any extra -actual arguments. +actual arguments. Arguments with default values that are followed by non-defaulted -arguments become required arguments (in 8.6 it will be considered an -error). +arguments become de-facto required arguments, though this may change +in a future version of Tcl; portable code should ensure that all +optional arguments come after all required arguments. +.PP There is one special case to permit procedures with variable numbers of arguments. If the last formal argument has the name -\fBargs\fR, then a call to the procedure may contain more actual arguments -than the procedure has formals. In this case, all of the actual arguments +.QW \fBargs\fR , +then a call to the procedure may contain more actual arguments +than the procedure has formal arguments. In this case, all of the actual arguments starting at the one that would be assigned to \fBargs\fR are combined into a list (as if the \fBlist\fR command had been used); this combined value is assigned to the local variable \fBargs\fR. @@ -63,8 +66,14 @@ When \fIbody\fR is being executed, variable names normally refer to local variables, which are created automatically when referenced and deleted when the procedure returns. One local variable is automatically created for each of the procedure's arguments. -Other variables can only be accessed by invoking one of the \fBglobal\fR, +Other variables can only be accessed by invoking one of the \fBglobal\fR, \fBvariable\fR, \fBupvar\fR or \fBnamespace upvar\fR commands. +The current namespace when \fIbody\fR is executed will be the +namespace that the procedure's name exists in, which will be the +namespace that it was created in unless it has been changed with +\fBrename\fR. +'\" We may change this! It makes [variable] unstable when renamed and is +'\" frankly pretty crazy, but doing it right is harder than it looks. .PP The \fBproc\fR command returns an empty string. When a procedure is invoked, the procedure's return value is the value specified in a @@ -74,28 +83,46 @@ executed in the procedure's body. If an error occurs while executing the procedure body, then the procedure-as-a-whole will return that same error. .SH EXAMPLES +.PP +This is a procedure that takes two arguments and prints both their sum +and their product. It also returns the string +.QW OK +to the caller as an explicit result. +.PP +.CS +\fBproc\fR printSumProduct {x y} { + set sum [expr {$x + $y}] + set prod [expr {$x * $y}] + puts "sum is $sum, product is $prod" + return "OK" +} +.CE +.PP This is a procedure that accepts arbitrarily many arguments and prints them out, one by one. +.PP .CS \fBproc\fR printArguments args { - foreach arg $args { - puts $arg - } + foreach arg $args { + puts $arg + } } .CE .PP This procedure is a bit like the \fBincr\fR command, except it multiplies the contents of the named variable by the value, which defaults to \fB2\fR: +.PP .CS \fBproc\fR mult {varName {multiplier 2}} { - upvar 1 $varName var - set var [expr {$var * $multiplier}] + upvar 1 $varName var + set var [expr {$var * $multiplier}] } .CE - .SH "SEE ALSO" info(n), unknown(n) - .SH KEYWORDS argument, procedure +'\" Local Variables: +'\" mode: nroff +'\" End: |