String Comparison

D overloads the binary relational operators and permits them to be used for string comparisons as well as integer comparisons. The relational operators perform string comparison whenever both operands are of type string, or when one operand is of type string and the other operand can be promoted to type string, as described in String Assignment. All of the relational operators can be used to compare strings:

Table 6-1 D Relational Operators for Strings

<	left-hand operand is less than right-operand
<=	left-hand operand is less than or equal to right-hand operand
>	left-hand operand is greater than right-hand operand
>=	left-hand operand is greater than or equal to right-hand operand
==	left-hand operand is equal to right-hand operand
!=	left-hand operand is not equal to right-hand operand

As with integers, each operator evaluates to a value of type int which is equal to one if the condition is true, or zero if it is false.

The relational operators compare the two input strings byte-by-byte, similar to the C library routine strcmp(3C). Each byte is compared using its corresponding integer value in the ASCII character set, as shown in ascii(5), until a null byte is read or the maximum string length is reached. Some example D string comparisons and their results are:

"coffee" < "espresso"	... returns 1 (true)
"coffee" == "coffee"	... returns 1 (true)
"coffee" >= "mocha"	... returns 0 (false)