clarified unbreakable latex output: Pretty.unformatted and (Pretty.string_of o Pretty.unbreakable) should coincide, but are produced by quite different means;
section "IMP --- A Simple Imperative Language"
theory Com imports BExp begin
datatype
com = SKIP
| Assign vname aexp ("_ ::= _" [1000, 61] 61)
| Seq com com ("_;;/ _" [60, 61] 60)
| If bexp com com ("(IF _/ THEN _/ ELSE _)" [0, 0, 61] 61)
| While bexp com ("(WHILE _/ DO _)" [0, 61] 61)
end