Richard Suchenwirth 2005-04-02 - lmap is a "collecting foreach" which returns a list of its results. In Jim it is built in, but it can be easily had in pure Tcl:
proc lmap {_var list body} {
upvar 1 $_var var
set res {}
foreach var $list {lappend res [uplevel 1 $body]}
set res
}Several usage examples are at Multiplication tables. Lmap is a compromise between Tcl and the classical functional programming function map, in that it takes a "quasi-lambda" which is split up into the _var name and the body arguments. However, this style is well-known from foreach, and somehow reads better:
lmap i {1 2 3 4 5} {expr $i*$i}vs.
map [lambda i {expr $i*$i}] {1 2 3 4 5}A cute variation is fmap (influenced by ApplyAll in Backus' FP; Joy has a comparable operator in cleave) which maps a list of functions on one argument:
proc fmap {functions x} {lmap f $functions {$f $x}}Then we can write a file reader like this:
proc << filename {lindex [fmap {read close} [open $filename]] 0}