# Binary Predicate

Category: functors | Component type: concept

### Description

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.

### Refinement of

Binary Function

### Associated types

Result type | The type returned when the Binary Predicate is called. The result type must be convertible to `bool`.

### Notation

`F` | A type that is a model of Binary Predicate
`X` | The first argument type of `F`
`Y` | The second argument type of `F`
`f` | Object of type `F`
`x` | Object of type `X`
`y` | Object of type `Y`

### Valid expressions

Name | Expression | Type requirements | Return type
--- | --- | --- | ---
Function call | `f(x,y)` |  | Convertible to `bool`

### Expression semantics

Name | Expression | Precondition | Semantics | Postcondition
--- | --- | --- | --- | ---
Function call | `f(x,y)` | The ordered pair `(x,y)` is in the domain of `f`. | Returns `true` if the condition is satisfied, `false` if it is not. | The result is either `true` or `false`.

### Complexity guarantees

### Invariants

### Models

- `bool (*)(int,int)`
- `equal_to`

### Notes

### See also

Predicate, Adaptable Predicate, Adaptable Binary Predicate

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