define_ggbash_constants has no side effect.
It is similar with the 'const' modifier in C or C++.
define_ggbash_constants()One thing to note is define_ggbash_constants set implicitly
the preference order of geom_name in ggplot2.
For example, 'p' ambiguously matches to geom_point
and geom_pointrange,
but ggbash automatically uses geom_point
with a warning message about the ambiguity.
This is a design choice based on the observation that
geom_point is often used
more frequently than geom_pointrange.
In order to use geom_pointrange,
at least 6 characters ('pointr') is needed.
The preference order is used when doing partial match in GgplotParser.