The Occurrences(x, L) command returns the number of entries in the list L which equal x using a boolean comparison.

If a function f is provided, equality is tested using f(x, L[i], opts) for each element $L_i$ in the list.

$\mathrm{with}\left(\mathrm{ListTools}\right)\:$

$L≔\left[3.263\,2.3\,6.255\,3.261\,3.262\right]$

$L≔\left[3.263\,2.3\,6.255\,3.261\,3.262\right]$

$\mathrm{Occurrences}\left(3.263\,L\right)$

$1$

$\mathrm{Occurrences}\left(3.263\,L\,\mathrm{verify}\,\mathrm{float}\left(10\,\mathrm{digits}=3\right)\right)$

$3$

$\mathrm{L2}≔\left[1\,2\,3\,4\,3\,4\,b\,b\,a\,c\,c\,c\right]\:$

$\mathrm{SortedList}≔\mathrm{sort}\left(\mathrm{L2}\&comma;\left(x\&comma;y\right)\mapsto \mathrm{ListTools}:-\mathrm{Occurrences}\left(y\&comma;\mathrm{L2}\right)<\mathrm{ListTools}:-\mathrm{Occurrences}\left(x\&comma;\mathrm{L2}\right)\right)$

$\mathrm{SortedList}≔\left[c\&comma;c\&comma;c\&comma;b\&comma;b\&comma;4\&comma;3\&comma;4\&comma;3\&comma;a\&comma;2\&comma;1\right]$

$\mathrm{ListTools}:-\mathrm{FindRepetitions}\left(\mathrm{SortedList}\&comma;\mathrm{ListTools}:-\mathrm{Occurrences}\left(\mathrm{SortedList}\left[1\right]\&comma;\mathrm{L2}\right)-1\right)$

$\left[c\right]$