= Translation of RSF-Files into DIMACS Format =

== Translation of Tristate Variables ==
Tristate variables will be translated into 2 variables. This translation shall be equal to the translation of Undertaker or !KConfigReader:
* One variable declaring whether the related KConfig variable is permanently selected
* One variable declaring whether the related KConfig variable is selected as a module.
* Only one of these variables can be selected at the same time.
The translation will be done as follows:
* In RSF:
{{{
Item VARIABLE tristate
}}}
* In DIMACS:
{{{
Not(VARIABLE) or Not(VARIABLE_MODULE)
}}}
* Meaning:
||'''VARIABLE'''||'''VARIABLE_MODULE'''||'''Explanation'''||
||0||0||VARIABLE is permanently deselected ('n' was selected)||
||1||0||VARIABLE is permanently selected ('y' was selected)||
||0||1||VARIABLE is selected as a module ('m' was selected)||
||1||1||Illegal state||

== Translation of ''depends'' Constraints ==
Each variable can have multiple depends statements, specifying when the variable can be configured. The variable must remain unconfigured (in case of a Boolean or Tristate variable, it must be set to ''n''), if none of the depends statements is fulfilled.
Conditions will be translated as follows:
1. One Condition:
 * In RSF:
{{{
depends Variable Condition
}}}
 * In Boolean formula:
{{{
Not(Condition) implies Not(Variable)
}}}
 * In DIMACS:
{{{
Condition or Not(Variable)
}}}
1. Multiple Conditions
 * In RSF:
{{{
depends Variable Condition1
depends Variable Condition2
}}}
 * In Boolean formula:
{{{
Not(Condition1) and Not(Condition2) implies Not(Variable)
}}}
 * In DIMACS:
{{{
Condition1 or Condition2 or Not(Variable)
}}}

== Translation of ''!ItemSelects'' Constraints ==
The [https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt KConfig specification] defines select statements as follows:
> reverse dependencies: "select" <symbol> !["if" <expr>]
>  While normal dependencies reduce the upper limit of a symbol (see
>  below), reverse dependencies can be used to force a lower limit of
>  another symbol. The value of the current menu symbol is used as the
>  minimal value <symbol> can be set to. If <symbol> is selected multiple
>  times, the limit is set to the largest selection.
>  Reverse dependencies can only be used with boolean or tristate
>  symbols.
1. Translation of Boolean !ItemSelect statements:
 * In RSF:
{{{
ItemSelects BOOLEAN_VAR OTHER_VAR CONDITION
}}}
 * In Boolean formula:
{{{
(BOOLEAN_VAR and CONDITION) implies OTHER_VAR
}}}
 * In DIMACS:
{{{
Not(BOOLEAN_VAR) or Not(CONDITION) or OTHER_VAR
}}}
2. Translation of Tristate !ItemSelect statements:
 * In RSF:
{{{
ItemSelects TRISTATE_VAR OTHER_VAR CONDITION
}}}
 * In Boolean formula:
{{{
(TRISTATE_VAR and CONDITION) implies OTHER_VAR
(TRISTATE_VAR_MODULE and CONDITION) implies OTHER_VAR_MODULE
}}}
 * In DIMACS:
{{{
Not(TRISTATE_VAR) or Not(CONDITION) or OTHER_VAR
Not(TRISTATE_VAR_MODULE) or Not(CONDITION) or OTHER_VAR_MODULE
}}}

== Ranges ==
Ranges of !Integers/Hex variables will not be considered. Since Kconfig supports only == and != comparisons, only values used in constraints will be translated to DIMACS.