master > master: codego - iff

codego/aussagenlogik/formulae/formulae_basic.go

@@ -145,3 +145,4 @@ func (fml Formula) IsConjunction() bool         { return fml.kind == "and" || fm
 func (fml Formula) IsDisjunction2() bool        { return fml.kind == "or2" }
 func (fml Formula) IsDisjunction() bool         { return fml.kind == "or" || fml.kind == "or2" }
 func (fml Formula) IsImplication() bool         { return fml.kind == "implies" }
+func (fml Formula) IsDoubleImplication() bool   { return fml.kind == "iff" }

codego/aussagenlogik/formulae/formulae_construction.go

@@ -115,3 +115,12 @@ func Implies(fml1 Formula, fml2 Formula) Formula {
 		subformulae: [](*Formula){&fml1, &fml2},
 	}
 }
+
+func DoubleImplication(fml1 Formula, fml2 Formula) Formula {
+	return Formula{
+		kind:        "iff",
+		expr:        "(" + fml1.expr + " <-> " + fml2.expr + ")",
+		valence:     2,
+		subformulae: [](*Formula){&fml1, &fml2},
+	}
+}

codego/aussagenlogik/recursion/recursion_eval.go

@@ -31,6 +31,8 @@ func Eval(fml formulae.Formula, I []string) int {
 				return utils.MaxList(prevValues)
 			} else if fml.IsImplication() {
 				return utils.BoolToInt(prevValues[0] <= prevValues[1])
+			} else if fml.IsDoubleImplication() {
+				return utils.BoolToInt(prevValues[0] == prevValues[1])
 			} else {
 				panic("Could not evaluate expression!")
 			}

codego/aussagenlogik/schema/schema.go

@@ -139,6 +139,11 @@ func (ant antlrTree) toFormula() formulae.Formula {
 		if nChildren == 3 {
 			return formulae.Implies(subants[0].toFormula(), subants[2].toFormula())
 		}
+	case "iff":
+		// NOTE: expr = expr <=> expr
+		if nChildren == 3 {
+			return formulae.DoubleImplication(subants[0].toFormula(), subants[2].toFormula())
+		}
 	case "and", "or":
 		// NOTE: expr = expr op expr op ... op expr
 		var n int = int((len(subants) + 1) / 2)