Typing

The typed variable concept refers to associating a data type with a variable, which defines what kind of values the variable can hold and what operations can be performed on it.

Typed variables are a fundamental feature in Rougail. Type validation is the first and most important quality check.

Strongly-typed

Rougail is a strongly-typed DSL.

This means that loading user data requires attention to the variable types.

The integrator define the variable type and the operator has to conform with it.

Dynamicaly-typed

During the structured data definition, the type is dynamic.

That is to say, the integrator can change the type of the variable at any time.

However, the operator who adapts the value does not have the possibility of redefining the type of the variable.

See also

the variable mutability

Type inference

Type inference is the process where Rougail automatically figures out the types without explicit annotations. In fact, the variable type comes from the type of its default value.

The type inference is in particular use with the short-hand notation.

Variables typing

Standard types

Rougail accepts the following standard types:

  • string (default type of a variable)

  • integer

  • float

  • boolean

See also

the variable documentation

Specialized types

But we will also find a whole series of specialized types:

  • IP

  • domainname

  • port

  • MAC

  • secret

  • …

See also

the variable documentation

A variable with a list of possible values

Sometimes a variable can only hold a finite list of possible values. We call it a variable with a list of possible values.

See also

The tutorial with a real world sample about a variable with a list of possible values

Type parameters

For certain types, there are a number of parameters that can be used to further type the variables.

See also

the variable documentation

Custom type

It is not possible to create every possible type of variable.

Therefore, it is necessary to provide a simple way to create these custom types.

There are two ways to create a type:

  • creating a Tiramisu type

  • creating a type from an existing variable, have a look at the tutorial with a real world sample custom type.

Nullable variable

The null type (or None in Python) does not exist in Rougail.

All variables, regardless of their type, can be nullable (see the remarks on the list type below).

Even if all types can accept this value, by default, they do not.

In reality, the variable not nullable with the value to null is not accessible in read-only mode (which is the case during the output steps). In read/write mode, the access is indeed granted.

See also

The tutorial with a real world sample about a nullable variable

The list type

A list is not a type either. It is a property of a variable. There is no such thing as a container type (like a python list type for instance). This means that all type can have multiple values in a list but it can only contain values of an unique type.

A multiple variable could be nullable. This means that null can be accepted as a value in the list (not permitted by default). But the multiple variable could also be without value (not permitted too by default).

See also

The tutorial with a real world sample about a multiple variable

Families typing

The mapping type

A mapping is a collection of key: value pairs.

This is a JSON example:

{
  "my_variable": "my_value"
}

In Rougail the mapping type is called a family. It is a container designed to hold variables.

The whole configuration tree structure is handled by the families definitions. It is possible to create subfamilies.

See also

the family documentation

The dynamically built family

A dynamically built family is a special family.

dynamically built family

A dynamically built family is a fictitious family linked to a list of unique identifiers.

This means that families will appear or disappear folling the context.

See also

the dynamically built family documentation

Homogeneous elements sequence

sequence
homogeneous elements sequence

A specific type of mapping, called a sequence, allows you to have a list of homogeneous objects.

For example, if I want to be able to create an unlimited number of users associated with a secret, you can’t use lists; I need a list of objects.

In JSON we will have:

[
     {
       "user": "login1",
       "secret": "MySecret"
     },
     {
       "user": "login2",
       "secret": "MySecret"
     }
]