• ← SetDelayed
• → TagSetDelayed

TagSet

WMA link

TagSet[f, expr, value]

f /: expr = value

assigns value to expr, associating the corresponding assignment with the symbol f.

Create an upvalue without using UpSet:

• • square /: area[square[s_]] := s^2

• • DownValues[square]

• • UpValues[square]

The symbol f must appear as the ultimate head of lhs or as the head of an element in lhs:

• • x /: f[g[x]] = 3;

• • g /: f[g[x]] = 3;

• • f[g[x]]