3 ms·

> The basic problem is, how do you even know that something is a variable reference? Isn't that by convention? Like there is a "upvar" to grab values of the pr

• int_19h 5y ago
  "upvar" is explicit, there's no guesswork involved there. But how would you handle a lambda with a body like this? if {$foo == 1} { puts $bar } else { puts $baz } given that all the {}s are just non-expanded string literals, and what makes them be interpreted as code is the implementation of "if"? Sure, you can hardcode "if"; but the whole point of Tcl is that syntax constructs like that can be easily implemented as a library, which breaks if you have to special-case them in lambdas for them to work. Now if you used upvar, this kinda sorta works, but only so long as the lambda is immediately invoked by the function that it was passed to. If you want to pass it on, you'd have to wrap it in another lambda. And, of course, this only works for lambdas that don't escape.