Add multiple clause and tree level optimizations

Implement optimizations that can be called in parallel or serial.
Optimizations occur mostly in place and result in a logically equivalent
tree when used correctly.

Optimizations
=============

* Sort - sort all statements within a clause tree
* Simplify - apply negation rules to all statements
* Flatten - merge child clauses with parents
* Compact - merge equivalent statements
* Tidy^ - remove zero statements
* Contradictions - zero contradicting statements and clauses
* StrictEquality - zero fuzzy statements when exact statements are within
  clause
* Tighten - combine multiple fuzzy statements to the least (AND) or
  most (OR) restrictive bounds

^: when used incorrectly can turn an invalid clause tree into a valid
one

1 files changed, 43 insertions, 1 deletions

diff --git a/pkg/util/util.go b/pkg/util/util.go
index a1dc37c..a525bca 100644
--- a/pkg/util/util.go
+++ b/pkg/util/util.go
@@ -1,6 +1,10 @@
 package util
 
-import "time"
+import (
+	"iter"
+	"slices"
+	"time"
+)
 
 func ParseDateTime(s string) (time.Time, error) {
 	dateFormats := []string{
@@ -33,3 +37,41 @@ func ParseDateTime(s string) (time.Time, error) {
 
 	return time.Time{}, err
 }
+
+// Create a copy of a slice with all values that satisfy cond
+func Fitler[E any](s []E, cond func(e E) bool) []E {
+	filtered := make([]E, 0, len(s))
+	for _, e := range s {
+		if cond(e) {
+			filtered = append(filtered, e)
+		}
+	}
+
+	return filtered
+}
+
+// Create an iterator of index and element for all values in a slice which satisfy cond.
+func FilterIter[E any](s []E, cond func(e E) bool) iter.Seq2[int, E] {
+	return func(yield func(int, E) bool) {
+		for i, e := range s {
+			if cond(e) {
+				if !yield(i, e) {
+					return
+				}
+			}
+		}
+	}
+}
+
+// FilterIter but backwards
+func BackwardsFilterIter[E any](s []E, cond func(e E) bool) iter.Seq2[int, E] {
+	return func(yield func(int, E) bool) {
+		for i := len(s) - 1; i >= 0; i-- {
+			if cond(s[i]) {
+				if !yield(i, s[i]) {
+					return
+				}
+			}
+		}
+	}
+}