[NTG-context] Define new symbol by stitching two symbols together

I would like to define new symbols by stitching together existing glyphs. This is what I have come up so far: \define[1]\Transition{-\!\![#1]\!\!\rightarrow} \starttext \m{L\Transition{A}R} \stoptext This should render as -[ ]->, ideally with no space between the dash or the arrow and the brackets, i.e., -[ should appear like a single glyph; ditto for ]-->. With the definition above, however, the space is variable, and in some circumstances the gliphs overlap. How can I improve the above definition? Nicola