File: MP.doc

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\DOC MP

\TYPE {MP : thm -> thm -> thm}

\SYNOPSIS
Implements the Modus Ponens inference rule.

\KEYWORDS
rule, modus ponens, implication.

\DESCRIBE
When applied to theorems {A1 |- t1 ==> t2} and {A2 |- t1},
the inference rule {MP} returns the theorem {A1 u A2 |- t2}.
{
    A1 |- t1 ==> t2   A2 |- t1
   ----------------------------  MP
          A1 u A2 |- t2
}

\FAILURE
Fails unless the first theorem is an implication whose antecedent is the
same as the conclusion of the second theorem (up to alpha-conversion).

\EXAMPLE
{
  # let th1 = TAUT `p ==> p \/ q`
    and th2 = ASSUME `p:bool`;;
  val th1 : thm = |- p ==> p \/ q
  val th2 : thm = p |- p

  # MP th1 th2;;
  val it : thm = p |- p \/ q
}

\SEEALSO
EQ_MP, MATCH_MP, MATCH_MP_TAC, MP_TAC.

\ENDDOC