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) |
