Tactic Notation
     "if" tactic(t)
     "then" tactic(t1)
     "else" tactic(t2) :=
     first [ t; first [ t1 | fail 2 ] | t2 ].

if t then t1 else t2 is equivalent to t; t1 if t does not fail and is equivalent to t2 otherwise.

if/then/else (tactical) (last edited 11-05-2008 00:22:30 by JeffVaughan)

Cocorico!WikiLicense