xspace – Define commands that appear not to eat spaces

The xs­pace pack­age pro­vides a sin­gle com­mand that looks at what comes af­ter it in the com­mand stream, and de­cides whether to in­sert a space to re­place one "eaten" by the TeX com­mand de­coder. The de­ci­sion is based on what came af­ter any space, not on whether there was a space (which is un­know­able): so if the next thing proves to be punc­tu­a­tion, the chances are there was no space, but if it's a let­ter, there's prob­a­bly a need for space. This tech­nique is not per­fect, but works in a large pro­por­tion of cases.
The pack­age is part of the tools bun­dle in the LaTeX re­quired dis­tri­bu­tion.