[Omake] Testing whether a target has been defined

[Jason Hickey]

malc wrote:
...
>>> <OMakeroot>
>>> .SUBDIRS: .
>>>     old-rule = $(rule)
>>>     rule(p1, p2, p3, p4, p5, p6) =
>>>         old-rule($(p1), $(p2), $(p3), $(p4), $(p5), $(p6))
>>>         export
>>>     a: :value: $`(println $@)
>>>         touch $@
>>>     .DEFAULT: a
>>> </OMakeroot>
...
> Btw. is it possible to extend p6(body) somehow, my naive attempts have
> been unsuccessful.

Wow, that makes a lot of sense.  Here is a trick that will work--but I 
think we should consider adding something simpler to OMake.

     get-body(x) =
        value $x

     rule(multiple, target, pattern, sources, options, body) =
         XTARGETS[] += $(target)
         x =
            get-body()
                apply($(fun $(body)))
                echo XXX
         old-rule($(multiple), $(target), $(pattern), $(sources), 
$(options), $x)
         export

The idea: when an an application has a body, the body is passed to the 
function as its first argument.  For example, consider the expression.

    get-body()
       echo Hi
       echo Bye

This evaluates to the body "echo Hi; echo Bye".

Similarly, the fun function takes a body as its first argument.  So 
$(fun $(body)) is a function of 0 arguments with body $(body), and the 
apply(...) applies the function.

I've attached a complete OMakefile.  I admit it is a bit crazy:b

Jason

-- 
Jason Hickey                  http://www.cs.caltech.edu/~jyh
Caltech Computer Science      Tel: 626-395-6568 FAX: 626-792-4257
-------------- next part --------------
old-rule = $(rule)

XTARGETS[] =

append-body(x) =
   value $x

rule(multiple, target, pattern, sources, options, body) =
    XTARGETS[] += $(target)
    new-body =
       append-body()
           apply($(fun $(body)))
           echo Second line >> $@
    old-rule($(multiple), $(target), $(pattern), $(sources), $(options), $(new-body))
    export

a:
    echo Building the program $@
    echo First line > $@

println($"Targets: $(XTARGETS)")