LEFT_PBETA : (thm -> thm)
STRUCTURE
PairRules
LIBRARY
pair
SYNOPSIS
Beta-reduces a top-level paired beta-redex on the left-hand side of an equation.
DESCRIPTION
When applied to an equational theorem, LEFT_PBETA applies paired beta-reduction at top level to the left-hand side (only). Variables are renamed if necessary to avoid free variable capture. 
    A |- (\x. t1) t2 = s
   ----------------------  LEFT_PBETA
     A |- t1[t2/x] = s

FAILURE
Fails unless the theorem is equational, with its left-hand side being a top-level paired beta-redex.
SEEALSO
RIGHT_BETA, PBETA_CONV, PBETA_RULE, PBETA_TAC, RIGHT_PBETA, RIGHT_LIST_PBETA, LEFT_LIST_PBETA
HOL  Kananaskis-13