bdlb_cstringequalto

Detailed Description

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Basic Use of bdlb::CStringEqualTo

Purpose

Provide a standard compatible equality predicate for C-strings.

Classes

• bdlb::CStringEqualTo: a standard compatible C-string equality predicate

See also

Description

This component provides a struct, bdlb::CStringEqualTo, that defines a functor that checks two null-terminated strings for equality using a case-sensitive string comparison, rather than simply comparing the two addresses (as the std::equal_to functor would do). This comparison functor is suitable for supporting C-strings as keys in unordered associative containers. Note that the container behavior would be undefined if the strings referenced by such pointers were to change value.

Usage

This section illustrates intended use of this component.

Example 1: Basic Use of bdlb::CStringEqualTo

The following snippets of code illustrate how to create and use a bdlb::CStringEqualTo object as a binary predicate for the standard library function bsl::equal to test that two ranges of null-terminated character strings are equal.

First, we create few sequences with null-terminated character strings, making sure that their elements have different memory addresses:

const char hello1[] = { 'h', 'e', 'l', 'l', 'o', 0};
const char hello2[] = { 'h', 'e', 'l', 'l', 'o', 0};
 
const char* arrayA[3] = { "A", "B", hello1 };
const char* arrayB[3] = { "A", "B", hello2 };

Now, use bdlb::CStringEqualTo() as a binary predicate to compare sequences:

bool bdlbEqualTo = bsl::equal(arrayA, arrayA+3, arrayB,
                              bdlb::CStringEqualTo());
bool bslEqualTo  = bsl::equal(arrayA, arrayA+3, arrayB,
                              bsl::equal_to<const char *>());

Finally, we observe that bdlb::CStringEqualTo compares character string by their values, while the default comparator compares addresses:

assert( true  == bdlbEqualTo );
assert( false == bslEqualTo );