Fluent APIs

[Russel Winder via Digitalmars-d-learn]

I am having a crisis of confidence. In two places I have structurally:

    datum.action()
      .map!(…)

and then the fun starts as I need to actually do a flatMap. In one of
the two places I have to:

    .array
    .joiner;

but in the other place I have to:

    .joiner
    .array;

in order to stop the compiler spewing out a mass of (to me anyway)
incomprehensible messages with types I have no knowledge of. So why
does the fluent API chain break in different ways in the two cases. A
Priori this seems like a breakage of the abstraction.

Full code is at
https://github.com/russel/ApproxGC/blob/master/source/main.d
The comparison is between the functions createGenerationsDeleteList and
createListOfPlaces.

Any help rebuilding my knowledge would be good.

Also error message comprehensible to programmers rather than compiler
writers  might help.

-- 
Russel.
=============================================================================
Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder at ekiga.net
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel at winder.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
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