GroupBy

GroupBy(list, head)

return an association where the elements of list are grouped by head(element)

GroupBy(assoc, head)

return an association where the rules of assoc are grouped by head(rule-value)

Examples

A hierachical GroupBy

>> expr = {{a}, {a, b}, {a, c}, {a, b, c, d}, {a, b, c, f}, {b, c}, {b, d}};

>> hg = Normal @ GroupBy(# /. {} -> Nothing , First -> Rest,  Function(x, hg(x, #2))) /. {Rule(a_, {b_}) :> Rule(a, b), Rule(a_, {}) :> #2(a)} &;

>> hg(expr, func)
{a->{b->c->{func(d),func(f)},func(c)},b->{func(c),func(d)}}

Implementation status

• ✅ - full supported

Github

• Implementation of GroupBy