reddit - lazy evaluation of function arguments

Manfred_Nowak svv1999 at
Tue Jul 1 01:01:05 PDT 2008

Georg Wrede wrote:

> (not too much reduction in code lines or complexity)

For me it is not a main goal to have few lines to read.
Often I found myself entangled in analyzing some code that turned out 
to be of minor priority because it only guarded the main aspect of the 
code from unusual cases. Putting those guards texually behind the main 
aspect of the code seems canonical, because it supports my way of 
turning to the main aspect first. 

So I tried to use the deferring capability of lazy parameters for 
annotating and beautifying this common pattern, but it turned out that 
the extra three lines are still too distracting.

        guarded( // the guards are actually evaluated here
    writefln( "This is the guarded part of the code.");
    writefln( "It is not executed if one of the boolean");
    writefln( "guards encounters that its expression");
    writefln( "evaluates to true.");
        (), // list of guards: 
        guard( false, writefln( "this is the always failing guard.")),
        guard( i==42, writefln( "this is a hitchhiking guard."))


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