Refactor: Speedup predicates and binary operation

Before predicates and binary ops reducers use series of `if ()` blocks
to match the keywords. However, if matched the currect `arg` get replaced
with evaluation result, so further `if (<match-another-keyword>)`
is just wasting time/resources.

This patch introduce a chain of `if` → `else if` → ..., so after
first match the loop restarts w/ the next argument.