public Expression CreatePair(BuiltinPair pair)
{
return new FreeSymbolExpression { Name = "_Pair", Tag = pair, Display = _PairDisplay };
}
public static bool RecognizePair(Expression expression, out BuiltinPair value)
{
// \f.f <FIRST> <SECOND> is Pair
value = null;
if (expression is AbstractionExpression)
{
var abs = (AbstractionExpression)expression;
if (abs.Right is ApplicationExpression)
{
var app1 = (ApplicationExpression)abs.Right;
if (app1.Left is ApplicationExpression)
{
var app2 = (ApplicationExpression)app1.Left;
if (app2.Left is BoundSymbolExpression)
{
var bound = (BoundSymbolExpression)app2.Left;
if (bound.Symbol == abs.Left)
{
// Pair
value = new BuiltinPair { First = app2.Right, Second = app1.Right };
return true;
}
}
}
}
}
return false;
}