String values may be used as operands of the comparison operators, although the expression evaluator tries to do comparisons as integer or floating-point when it can. If one of the operands of a comparison is a string and the other has a numeric value, the numeric operand is converted back to a string using the C sprintf format specifier %d for integers and %g for floating-point values. For example, the commands

expr {"0x03" > "2"}

expr {"0y" < "0x12"}

both return 1. The first comparison is done using integer comparison, and the second is done using string comparison after the second operand is converted to the string 18. Because of Tcl’s tendency to treat values as numbers whenever possible, it isn’t generally a good idea to use operators like = = when you really want string comparison and the values of the operands could be arbitrary; it’s better in these cases to use the string compare command instead.