= Translation of RSF-Files into DIMACS Format =
[[PageOutline(2-5, Table of Contents, pullout)]]

== 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 String, Integer, Hex Variables ==
=== Concrete Values ===
For String, Integer, and Hex variables we list all used values as different variables in the following form:
{{{
VARIABLE=<value>
}}}
For a not configured variable (or an empty String) a variable in the following form will be created:
{{{
VARIABLE=n
}}}
Further, constraints must ensure that exactly one variable will be selected:
* In Boolean formula:
{{{
VARIABLE=n XOR VARIABLE=value1 XOR ... XOR VARIABLE=valueN
}}}
* In DIMACS:
{{{
Not(VARIABLE=n) OR Not(VARIABLE=value1)
Not(VARIABLE=n) OR (VARIABLE=value2)
...
Not(VARIABLE=n) OR (VARIABLE=valueN)
Not(VARIABLE=value1) OR (VARIABLE=value2)
...
Not(VARIABLE=value1) OR (VARIABLE=valueN)
...
VARIABLE=n OR VARIABLE=value1 OR ... OR VARIABLE=valueN
}}}
All combinations of 2 negated variables + 1 constraint were all variables are used in a positive combination.
=== 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.

== 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)
}}}
1. Variable depends of Tristate
 * In RSF:
{{{
depends VARIABLE TRISTATE_VAR
}}}
 * In Boolean formula:
{{{
Not(TRISTATE_VAR) and Not(TRISTATE_VAR_MODULE) implies Not(VARIABLE )
}}}
 * In DIMACS:
{{{
TRISTATE_VAR or TRISTATE_VAR_MODULE or Not(VARIABLE )
}}}
1. Tristate variable depends of Condition
 * In RSF:
{{{
depends TRISTATE_VAR CONDITION
}}}
 * In Boolean formula:
{{{
Not(CONDITION) implies Not(TRISTATE_VAR)
Not(CONDITION) implies Not(TRISTATE_VAR_MODULE)
}}}
 * In DIMACS:
{{{
CONDITION or Not(TRISTATE_VAR)
CONDITION or Not(TRISTATE_VAR_MODULE_VAR)
}}}

== 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
}}}