The procedure symmdiff is used for the set symmetric difference operator, which is defined by symmdiff(a,b)=(a union b) minus (a intersect b), for two arguments and associates to the left for more arguments.

$\mathrm{symmdiff}\left(\left\{a\right\}\,\left\{b\right\}\right)$

$\left\{a\,b\right\}$

$\mathrm{symmdiff}\left(\left\{a\,b\right\}\,\left\{b\,c\right\}\right)$

$\left\{a\,c\right\}$

$\mathrm{symmdiff}\left(\left\{a\,b\right\}\,\left\{a\,b\right\}\right)$

$\varnothing$

$\mathrm{symmdiff}\left(\left\{1\,2\,3\,4\right\}\,\left\{2\,4\,5\,6\right\}\,\left\{3\,4\,5\,7\right\}\right)$

$\left\{1\,4\,6\,7\right\}$

$\mathrm{symmdiff}\left(\left\{1\,2\,3\,4\right\}\,\left\{2\,4\,5\,6\right\}\right)$

$\left\{1\,3\,5\,6\right\}$

$\mathrm{symmdiff}\left(\left\{1\,3\,5\,6\right\}\,\left\{3\,4\,5\,7\right\}\right)$

$\left\{1\,4\,6\,7\right\}$

$\mathrm{symmdiff}\left(\left\{1\,3\,4\,5\right\}\,\left\{3\,5\right\}\,\left\{2\,4\,5\right\}\,\left\{3\,4\,5\right\}\,\left\{2\,4\,5\right\}\right)$

$\left\{1\,3\,5\right\}$