supprot predicate keyword

[zjhmale]

i wonder if we can use both keyword and symbol to present predicates, this is really useful when we construct queries with predicate in a macro, make the code more readable.

[zjhmale]

@immoh @ibdknox @AlexBaranosky

[immoh]

This looks useful. Maybe the implementation could be simplified so that we have both symbols and keywords in one map and there wouldn't be need to check two maps?

[zjhmale]

ok, that sounds cool, let me fix it.

[zjhmale]

done @immoh

[immoh]

Please squash the commits into a single one and I'll merge this.

[zjhmale]

ok, just a minute.

[zjhmale]

done. @immoh

[immoh]

Thanks!

[zjhmale]

my pleasure :)