With Digraph (see below), the line is converted to:
int _$[]={-!.0,};
On the right hand side, .0 is the double literal, ! is the logical negation operator, - is the arithmetic negation operator, and , is the trailing comma. Together {-!.0,} is an array initializer.
The left hand side int _$[] defines an int array. However, there’s one last problem, _$ is not a valid identifier in standard C. Some compilers (e.g, gcc) supports it as extension.
C11 ยง6.4.6 Punctuators
In all aspects of the language, the six tokens
<: :> <% %> %: %:%:behave, respectively, the same as the six tokens
[ ] { } # ##