4 Jan 2006 - Googie - Here's some very simple way to use set command like the following:
set a 5 set b $a + 3 + ($a * 2) puts $b
'$b' will be 18. The only requirement is to use 'mathematical' set case with more than 1 and 2 arguments (which are number of arguments for default set syntax). In practise it means that you have to do at least one white-space in math expression, or set will be interpreted as the Tcl-built-in one. Here's code to enable such functionality:
rename ::set ::set.org
proc ::set {var args} {
if {[llength $args] > 1} {
uplevel [list ::set.org $var [eval expr "{$args}"]]
} else {
uplevel [list ::set.org $var [lindex $args 0]]
}
}RS: Cute. But the case of [llength $args]==0 should also be covered as returning the value - right now it would set it to {}. Also, all the efficiency gained with braced expressions is of course lost here...
WHD: I prefer "let", as in
let b {$a + 3 + ($a * 2)}or especially
let x {$x + 1.5}Implemented in C, it's also reasonably fast.
escargo 10 Jan 2006 - I kind of like that distinction (that is, between set and let). (Maybe because I was exposed to some form of BASIC in ancient times.) It certainly is less typing to write
let x {$x + 1.5}than
set x [expr {$x + 1.5}]What about allowing bare words to dispense with the $? (Since the braced expression is a right hand side, after all.) That would give
let x {x + 1.5}Is that too radical a change? RS: It might cause conflicts between functions and arrays:
let x {sin(x)+cos(y)}NEM likes adding a touch more sugar and having:
let x = {$x + 1.5}