Standard Template Library Programmer's Guide

Adaptable Predicate, Binary Predicate, Adaptable Binary Predicate

Category: functors

Component type: concept

A Binary Predicate is a Binary Function whose result represents the truth or falsehood of some condition. A Binary Predicate might, for example, be a function that takes two arguments and tests whether they are equal.

Binary Function

FA type that is a model of Binary Predicate

XThe first argument type of F

YThe second argument type of F

fObject of type F

xObject of type X

yObject of type Y

• bool (*)(int,int)

• equal_to

Predicate, Adaptable Predicate, Adaptable Binary Predicate

Category: functors

Component type: concept

An Adaptable Predicate is a Predicate that is also an Adaptable Unary Function. That is, it is a Unary Function whose return type is bool , and that includes nested typedef s that define its argument type and return type.

Predicate, Adaptable Unary Function

None, except for those associated with Predicate and Adaptable Unary Function.

None, except for those defined by the Predicate and Adaptable Unary Function requirements.

• logical_not

• unary_negate

Predicate, Binary Predicate, Adaptable Binary Predicate

Category: functors

Component type: concept

An Adaptable Binary Predicate is a Binary Predicate that is also an Adaptable Binary Function. That is, it is a Binary Function whose return type is bool , and that includes nested typedef s that define its argument types and return type.

Predicate, Adaptable Binary Function

None, except for those associated with Predicate and Adaptable Binary Function.

None, except for those defined by the Predicate and Adaptable Binary Function requirements.

• less

• equal_to

• logical_and

• logical_or

• binary_negate

Binary Predicate, Predicate, Adaptable Predicate

Category: functors

Component type: concept

A Strict Weak Ordering is a Binary Predicate that compares two objects, returning true if the first precedes the second. This predicate must satisfy the standard mathematical definition of a strict weak ordering . The precise requirements are stated below, but what they roughly mean is that a Strict Weak Ordering has to behave the way that "less than" behaves: if a is less than b then b is not less than a , if a is less than b and b is less than c then a is less than c , and so on.

Binary Predicate

FA type that is a model of Strict Weak Ordering

XThe type of Strict Weak Ordering's arguments.

fObject of type F

x, y, zObject of type X

• Two objects x and y are equivalent if both f(x, y) and f(y, x) are false. Note that an object is always (by the irreflexivity invariant) equivalent to itself.

None, except for those defined in the Binary Predicate requirements.

• less

• less

• greater

• greater

[1] The first three axioms, irreflexivity, antisymmetry, and transitivity, are the definition of a partial ordering ; transitivity of equivalence is required by the definition of a strict weak ordering . A total ordering is one that satisfies an even stronger condition: equivalence must be the same as equality.