# getparams.tcl
 # Copyright 2001 by Larry Smith
 # Wild Open Source, Inc
 # license terms: GPL
 # Takes a list of variable-value pairs and creates and
 # initializes the former with the latter in the calling
 # context.  Then parses the $argv in the calling context
 # for "-var value" pairs and updates any vars mentioned
 # there.  It will not create vars not mentioned in the
 # initializing list.

 proc getparams { args } {
   upvar args arglist

   if { [ llength $arglist ] == 0 } return
   if { [ llength $arglist ] == 1 } {
     # braced set of args
     eval set arglist $arglist
   }
   set varlist {}
   foreach { var val } $args {
     uplevel 1 set $var \{$val\}
     lappend varlist $var
   }
   foreach { var val } $arglist {
     set var [ string range $var 1 end ]
     if { [ lsearch $varlist $var ] != -1 } {
       uplevel 1 set $var \{$val\}
     }
   }
 }

Test:

  proc foo { args } {
    set d 4
    getparams a 1 b 2 c 3
    puts "a is $a, b is $b, c is $c, d is $d"
  }


  foo -a 100 -b 200
  foo -b 200 -a 100
  foo -c 300 -d 400

result:

 a is 100, b is 200, c is 3, d is 4
 a is 100, b is 200, c is 3, d is 4
 a is 1, b is 2, c is 300, d is 4

Notice it refused to allow setting "d" - d was not
specified as a parameter.

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[[ [Category Argument Processing] ]]