class - What is predicate in C++?

Question

question from:https://stackoverflow.com/questions/5921609/what-is-predicate-in-c

Answer 1

A predicate is a C++ function returning a boolean or an object having a bool operator() member. A unary predicate takes one argument, a binary takes two, and so on. Examples of questions predicates can answer for a particular algorithm are:

• Is this element what we are looking for?
• Is the first of two arguments ordered first in our order?
• Are the two arguments equal?

Almost all STL algorithms take a predicate as last argument.

You can construct new predicates using standard, self-defined, and/or predicate-making classes (here is a good reference).