[isabelle] Precedences of map_upd vs. fun_upd



Dear all,

In Isabelle/HOL, function update has the syntax f(x := y) and map update uses f(x |-> y). Surprisingly, the syntaxes have different precedences. Function update uses

  "_Update"        :: ['a, updbinds] => 'a            ("_/'((_)')" [1000,0] 900)

and map update uses

  "_MapUpd"  :: "['a ~=> 'b, maplets] => 'a ~=> 'b" ("_/'(_')" [900,0]900)

Consequently, Isabelle accepts the term "f x(1 |-> 2)", but not "f x(1 := Some 2)". The latter has to parenthesized as in "(f x)(1 := Some 2)".

Browsing the repository, I found that Tobias added the map syntax in 2003 (d2e550609c40) and that David von Oheimb has changed the precedences for function update in 2000 (666d3a4f3b9d). Before that, precedences for function update were the same as they are now for maps.

Can anyone remember why David changed the precedences and why Tobias used the older precedences when he introduced the syntax for maps? Why are the precedences not the same? And should they be unified?

Andreas







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