As of tcl8.5, Tcl has native support for lambda, provided by means of apply per TIP 194 [L1 ].
The apply command is documented here http://www.tcl.tk/man/tcl8.5/TclCmd/apply.htm
This enables the following:
proc lambda {arglist body {ns {}}} {
list ::apply [list $arglist $body $ns]
}An example of its use:
set q [lambda {x} {incr x}]
{*}$q 1
% 2The significant thing here is that (in the above example) $q will contain an anonymous proc which will byte compile itself. So subsequent invocations of {*}$q will not incur a recompilation. The anonymous proc will persist as long as it's not shimmered away, and can be passed around as a value!
This is ubercool - guilt-free lambda.
NEM notes also that in many places where lambdas are useful, the explicit {*} is not necessary -- e.g. most commands which accept callbacks will automatically expand the command anyway:
% lsort -command [lambda {x y} {
expr {[string length $x] < [string length $y]}
}] "My name is Neil"
name Neil My is
% trace add variable ::foo write [lambda args {
puts "foo = $::foo"
}]
% set foo 12
foo = 12
12[ Category Example ]