Component bdlb_cstringequalto [Package bdlb]

Provide a standard compatible equality predicate for C-strings. More...

Namespaces
namespace	bdlb

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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 );