master > master: codego - Formulae package

codego/aussagenlogik/formulae/formulae_construction.go

@@ -47,9 +47,16 @@ func Generic(name string) Formula {
 }
 
 func Negation(fml Formula) Formula {
+	var name string
+	if fml.IsAtom() {
+		name = fml.GetName()
+	}
+	var expr = fml.expr
+	expr = "!" + expr
 	return Formula{
 		kind:        "not",
-		expr:        "!" + " " + fml.expr,
+		name:        name, // preserves name of negated atoms
+		expr:        expr,
 		valence:     1,
 		subformulae: [](*Formula){&fml},
 	}
@@ -65,20 +72,26 @@ func Conjunction2(fml1 Formula, fml2 Formula) Formula {
 }
 
 func Conjunction(fmls []Formula) Formula {
+	switch len(fmls) {
+	case 0:
+		return Tautology
+	case 1:
+		return fmls[0]
+	}
 	var expr string = ""
-	var children = make([](*Formula), len(fmls))
+	var subFmls = make([](*Formula), len(fmls))
 	for i, fml := range fmls {
+		(func(i int, subFml Formula) { subFmls[i] = &subFml })(i, fml)
 		if i > 0 {
 			expr += " && "
 		}
 		expr += fml.expr
-		children[i] = &fml
 	}
 	return Formula{
 		kind:        "and",
 		expr:        "(" + expr + ")",
-		valence:     len(children),
-		subformulae: children,
+		valence:     len(subFmls),
+		subformulae: subFmls,
 	}
 }
 
@@ -92,20 +105,26 @@ func Disjunction2(fml1 Formula, fml2 Formula) Formula {
 }
 
 func Disjunction(fmls []Formula) Formula {
+	switch len(fmls) {
+	case 0:
+		return Contradiction
+	case 1:
+		return fmls[0]
+	}
 	var expr string = ""
-	var children = make([](*Formula), len(fmls))
+	var subFmls = make([](*Formula), len(fmls))
 	for i, fml := range fmls {
+		(func(i int, subFml Formula) { subFmls[i] = &subFml })(i, fml)
 		if i > 0 {
 			expr += " || "
 		}
 		expr += fml.expr
-		children[i] = &fml
 	}
 	return Formula{
 		kind:        "or",
 		expr:        "(" + expr + ")",
-		valence:     len(children),
-		subformulae: children,
+		valence:     len(subFmls),
+		subformulae: subFmls,
 	}
 }