Pattern matching Inequality

问题

I'd like to extract arguments from instances of Inequality. Following doesn't work, any idea why and how to fix it?

Inequality[1, Less, x, Less, 2] /. Inequality[a_, _, c_, _, e_] -> {a, c, e}

回答1:

Inequality[1,Less,x,Less,2] /. HoldPattern[Inequality[a_,_,b_,_,c_]] -> {a, b, c}


Out: {1, x, 2}

回答2:

Also, you can do this:

Inequality[1, Less, x, Less, 2] /. Literal @ Inequality[ a_ , _ , c_ , _ , e_ ] -> {a, c, e}

ADL

回答3:

Why don't you use standard access to subexpression?

expr = Inequality[1, Less, x, Less, 2]; {a,c,e} = {expr[[1]], expr[[3]], expr[[5]]};

来源：https://stackoverflow.com/questions/3851390/pattern-matching-inequality