½≠1/2;

if ½≠1/2 then
     error ("The number 1/2 isn't properly substituted.")$    

if x²≠x^2 then
     error ("The exponent 2 isn't properly substituted.")$    

if x³≠x^3 then
     error ("The exponent 3 isn't properly substituted.")$    

if √(2)≠sqrt(2) then
     error ("The square root isn't properly substituted.")$    

if ⅈ≠%i then
     error ("The imaginary unit isn't properly substituted.")$    

if ⅇ≠%e then
     error ("Euler's constant isn't properly substituted.")$    

if ⇒≠implies then
     error ("The \"implies\" symbol isn't properly substituted.")$    

if ∞≠inf then
     error ("The \"infinity\" symbol isn't properly substituted.")$    

if ∅≠[] then
     error ("The \"empty set\" symbol isn't properly substituted.")$    

/* if (a ⊻ b) ≠ (a xor b) then 
    error("Error substituting the \"xor\" operator")$ */;

if (a ⋀ b) ≠ (a and b) then 
    error("Error substituting the \"and\" operator")$

if (¬a) ≠ (not a) then 
    error("Error substituting the \"not\" operator")$

if (a ⋁ b) ≠ (a or b) then 
    error("Error substituting the \"or\" operator")$

if ∫≠integrate then
     error ("The \"integrate\" symbol isn't properly substituted.")$    

if ∫≠integrate then
     error ("The \"integrate\" symbol isn't properly substituted.")$    

if (2 ≥ 3)  then 
    error("Error substituting the \">=\" operator")$

if (a ≤ b) ≠ (a <= b) then 
    error("Error substituting the \"<=\" operator")$

if ∑≠sum then
     error ("The \"sum\" symbol isn't properly substituted.")$    

if ∏≠product then
     error ("The \"product\" symbol isn't properly substituted.")$