5 Expressions [expr]

5.9 Relational operators [expr.rel]

The relational operators group left-to-right. [ Example: a<b<c means (a<b)<c and not (a<b)&&(b<c).  — end example ]

    relational-expression < shift-expression
    relational-expression > shift-expression
    relational-expression <= shift-expression
    relational-expression >= shift-expression

The operands shall have arithmetic, enumeration, or pointer type. The operators < (less than), > (greater than), <= (less than or equal to), and >= (greater than or equal to) all yield false or true. The type of the result is bool.

The usual arithmetic conversions are performed on operands of arithmetic or enumeration type. If both operands are pointers, pointer conversions ([conv.ptr]) and qualification conversions ([conv.qual]) are performed to bring them to their composite pointer type (Clause [expr]). After conversions, the operands shall have the same type.

Comparing pointers to objects is defined as follows:

  • If two pointers point to different elements of the same array, or to subobjects thereof, the pointer to the element with the higher subscript compares greater.

  • If one pointer points to an element of an array, or to a subobject thereof, and another pointer points one past the last element of the array, the latter pointer compares greater.

  • If two pointers point to different non-static data members of the same object, or to subobjects of such members, recursively, the pointer to the later declared member compares greater provided the two members have the same access control (Clause [class.access]) and provided their class is not a union.

If two operands p and q compare equal ([expr.eq]), p<=q and p>=q both yield true and p<q and p>q both yield false. Otherwise, if a pointer p compares greater than a pointer q, p>=q, p>q, q<=p, and q<p all yield true and p<=q, p<q, q>=p, and q>p all yield false. Otherwise, the result of each of the operators is unspecified.

If both operands (after conversions) are of arithmetic or enumeration type, each of the operators shall yield true if the specified relationship is true and false if it is false.