Hi Rick,
thanks for the ideas :)
However, as Mike Pechkin wrote, I do also believe that such a construct
is rather useless.
The examples are too simple. They can be easily rewritten as:
> (if-let X 13 (- X 1) 0) #-> 12
(if 13 (dec @) 0)
> (if-let X 13 (- X 1)) #-> 12 # you can leave off the Else clause.
(if 13 (dec @))
> (if-let X 0 (+ 42 X) -1) #-> 42 # because 0 is "truthy".
(if 0 (+ @ 42) -1)
and so on ..
Can you provide an example where it is shorter with 'if-let' than with
existing flow functions?
Note that you can always do
(if (condition)
(let X @
(do-something 1) )
(do-something 2)
(do-something 3) )
> # A definition
> (de if-let "Args"
> ## Better than anaphoric `if` because you can name the test result
> ## yourself.
> (let ((@Pattern "Test" @Then @Else) "Args"
> @Test-Result (eval "Test"))
> (eval
> (fill
> '(if @Test-Result
> (let (@Pattern @Test-Result)
> @Then)
> @Else)
> '(@Pattern @Test-Result @Then @Else)))))
This is a very un-PicoLisp-ish solution. It is a huge overhead to
rebuild the whole expression with 'fill' each time it is called.
Instead, you need to interprete it directly:
(de if-let "Args"
(if (eval (cadr "Args"))
(bind (car "Args")
(set (car "Args") @)
(eval (caddr "Args")) )
(run (cdddr "Args")) ) )
: (if-let X (* 3 4) (inc X) "Nope")
-> 13
: (if-let X NIL (inc X) "Nope")
-> "Nope"
♪♫ Alex
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