Hmm, so having a right-hand nildaic function passed to an operator simply
doesn't work. Oh well, makes sense once you think about it. :-)
This was all part of experimentation I was playing around with while
thinking about the power operator. Have you given that one any thought yet?
Regards,
Elias
On 29 July 2014 19:55, Juergen Sauermann <juergen.sauerm...@t-online.de>
wrote:
> Hi Elias,
>
> this is because your lambdas are niladic. The right lambda is called
> before SEL,
> while the left lambda is called by SEL. From SEL's perspective, 'then'; is
> a function
> while 'else' is a value.
>
> /// Jürgen
>
>
>
> On 07/29/2014 07:21 AM, Elias Mårtenson wrote:
>
> I was writing an operator that acts as an "if"-statement, calling one of
> two functions depending on the value of the argument:
>
> ∇Z ← (then SEL else) arg
> →(arg=1)/do¯then
> →(arg=0)/do¯else
> ⎕ES 'Illegal value for arg'
> →0
> do¯then:
> Z ← then arg
> →0
> do¯else:
> Z ← else arg
> ∇
>
> Note that the then and else functions are called with an argument "arg".
> When I call this operator with two nihilic lambda functions, I get very
> strange behaviour:
>
> * ⊣ ({⎕←'was true'} SEL {⎕←'was false'}) 0*
> was false
> * ⊣ ({⎕←'was true'} SEL {⎕←'was false'}) 1*
> was false
> was true
>
> I would expect to get an error message here, or perhaps seeing (⎕NC '⍵')
> to be 0. I certainly didn't expect to see both functions be called. My
> suspicion is that there is a problem with the parser somewhere, but I think
> Jürgen will have to look at this one.
>
> Regards,
> Elias
>
>
>
