I want to show informally a partial function in terms of mappings (not mentioning the function symbol or its domain, etc.)
a ↦ b, c ↦ e,
What is the best practice to informally show unmapped elements? My current versions are:
- d ↦ ⊥
- d ↦ ∅
(2) is nice because it intuitively says that d is mapped to nothing, but it says that it is mapped to a set while all other elements are mapped to variables.
(1) is nice because it shows that d is mapped to some distinguished entity (falsity), not a set. But this might be bit confusing as not may knows what bottom is.
Any suggestions?