"Testing infixform"
clear
check(infixform(1/x) == "1 / x")
check(infixform(x^2) == "x^2")
check(infixform(x^(-2)) == "1 / x^2")
check(infixform(sin(x)^2) == "sin(x)^2")
check(infixform(3^x) == "3^x")
check(infixform((-3)^x) == "3^x (-1)^x")
check(infixform((1/3)^x) == "3^(-x)")
check(infixform((-1/3)^x) == "3^(-x) (-1)^x")
check(infixform(1.2^x) == "(1.2)^x")
check(infixform((1.2 10^9)^x) == "(1.2 10^9)^x")
check(infixform((1.2 10^(-9))^x) == "(1.2 10^(-9))^x")
check(infixform((a+b)^x) == "(a + b)^x")
check(infixform((a+b)/(c+d)) == "a / (c + d) + b / (c + d)")
check(infixform(2/3 x/y) == "2 x / (3 y)")
check(infixform(-2/3 x/y) == "-2 x / (3 y)")
check(infixform((a,b,c)) == "(a,b,c)")
check(infixform(((a,b),(c,d))) == "((a,b),(c,d))")
check(infixform(quote((a+b)/(c+d))) == "(a + b) / (c + d)")
check(infixform(x^(a+b)) == "x^(a + b)")
check(infixform(x^(a b)) == "x^(a b)")
check(infixform(x^(a^b)) == "x^(a^b)")
check(infixform(x^(n!)) == "x^(n!)")
check(infixform(x^sin(x)) == "x^sin(x)")
