Implement LaTeX accent macros
Pyth, 51 46 45 43 41 40 bytes
I remove the curly braces and split at \, just like Reto Koradi's CJam answer does. The codes bar, dot and hat are recognized simply by the last decimal digit of the character code of the first character, modulo 3. I just add barf (RIP) &quot;&quot;&quot;&quot; to the first part and remove it in the end to save the code for handling the first part specially.
jtMsMCm,+@&quot;.^_&quot;eChd*\ -ld4&gt;d3c-+*4Nz`H\\

Try it online. Test suite.