All Ordered Bound Operations

All Ordered Bound Operations

A compact scan page for lower_bound, upper_bound, equal_range, and related ordered-lookup operations across sorted ranges and ordered containers.

How to use this reference page

Use reference pages to confirm names, categories, nearby facilities, and the constraints that matter before writing or reviewing code.

Scan the top of the page first to identify the primary types, functions, or algorithm families involved.
Use the nearby-page links when your question is really about a companion header, related algorithm family, or broader subsystem.
Validate tricky behavior with a small compileable example before relying on memory for details like invalidation, ordering, allocation, or lifetime rules.

All Ordered Bound Operations

Core bound operations

lower_bound
upper_bound
equal_range
binary_search

Where they appear

ordered associative containers such as map and set
classic <algorithm> sorted-range algorithms
ranges-based ordered lookup algorithms

Mental model

lower_bound: first element not less than the key
upper_bound: first element greater than the key
equal_range: pair of lower/upper bounds for equivalent values

Practical rules

These operations assume sorted data under the same comparator semantics.
Bound operations are often more informative than plain membership checks because they identify insertion positions.
For multi-key scenarios, equal_range is often the clearest choice.

Example in practice

#include <map>
#include <string>

int main() {
    std::map<std::string, int> counts{std::pair{"Ada", 1}, std::pair{"Bjarne", 2}};
    auto [it, inserted] = counts.insert({"Grace", 3});
    return inserted ? it->second : 1;
}