File: EXPAND_TAC.doc

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\DOC EXPAND_TAC

\TYPE {EXPAND_TAC : string -> tactic}

\SYNOPSIS
Expand an abbreviation in the hypotheses.

\DESCRIBE
The tactic {EXPAND_TAC "x"}, applied to a goal, looks for a hypothesis of the 
form {`t = x`} where {x} is a variable with the given name. It then replaces 
{x} by {t} throughout the conclusion of the goal.
 
\FAILURE
Fails if there is no suitable assumption in the goal.

\EXAMPLE
Consider the final goal in the example given for {ABBREV_TAC}:
{
  val it : goalstack = 1 subgoal (1 total)

   0 [`12345 + 12345 = n`]

  `n + f n = f n`
}
\noindent If we expand it, we get:
{
  # e(EXPAND_TAC "n");;
  val it : goalstack = 1 subgoal (1 total)
  
   0 [`12345 + 12345 = n`]
  
  `(12345 + 12345) + f (12345 + 12345) = f (12345 + 12345)`
}

\SEEALSO
ABBREV_TAC.

\ENDDOC