Triangle, tacit 1             Tc

        ----------------------
        s =. ( a + b + c ) % 2
        a < s
        b < s
        c < s
        ----------------------

Solution 2:  Remove reference to s:   
   Ttest =. ' *. / y. < 0.5 * +/ y. ' : ''

But this is still not functional style, because variable "y." is mentioned.
   sum =. +/
   f1 =. 0.5 & * @ sum
   f1
+---------+-+---+
|+---+-+-+|@|sum|
||0.5|&|*|| |   |
|+---+-+-+| |   |
+---------+-+---+

