== Why is this an issue?

Using the same value on both sides of a binary operator is a code defect. In the case of logical operators, it is either a copy/paste error and, therefore, a bug, or it is simply duplicated code and should be simplified. In the case of most binary mathematical operators, having the same value on both sides of an operator yields predictable results and should be simplified as well.

=== Exceptions

The following are ignored:

* When an increment or decrement operator is used, ex: ``+++*p++ == *p+++++``
* Bitwise operators `|, &, ^, <<`
* Arithmetic operators `+, *`
* Assignment operators `=, +=, *=`

=== Code examples

==== Noncompliant code example

[source,cpp]
----

void foo(int a, int b) {
  if ( a == a ) { // Noncompliant: always true
    // ...
  }
  
  if ( a != a ) { // Noncompliant: always false
    // ...
  }

  if ( (a == b) && (a == b) ) { // Noncompliant: if the first condition is true, the second one is too
    // ...
  }
  
  if ( (a == b) || (a == b) ) { // Noncompliant: if the first condition is true, the second one is too
    // ...
  }

  if ( 5 / 5 ) { // Noncompliant: always 1
    // ...
  }
  
  if ( 5 - 5 ) { // Noncompliant: always 0
    // ...
  }
}
----

== Resources

=== Standards

* https://wiki.sei.cmu.edu/confluence/x/5dUxBQ[CERT, MSC12-C.] - Detect and remove code that has no effect or is never executed

=== Related rules

* S1656 detects self-assignments

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