Why is this an issue?

Using constants instead of hard-coded numeric values improve readability and maintainability.

Note that the following structures and not checked against this rule:

• Constant declaration
• Variable declaration
• Type declaration
• Signal declaration
• Generic clause
• Port clause

How to fix it

Code examples

Noncompliant code example

architecture a of e is
begin
  output <= d1 when input = 3 -- Noncompliant: '3' hard-coded value
    else d2 when input = 4 -- Noncompliant: '4' hard-coded value
    else d3;
end;

Compliant solution

architecture a of e is
  constant fly : integer := 3; -- Compliant: '3' is part of constant declaration
  constant dream : integer := 4; -- Compliant: '4' is part of constant declaration

begin
  output <= d1 when input = fly
    else d2 when input = dream
    else d3;
end;