From ca161b26e9b6a253837e5ec4e0cf318bd0ee7903 Mon Sep 17 00:00:00 2001
From: Charlie Stanton <charlie@shtanton.xyz>
Date: Wed, 19 Apr 2023 13:58:13 +0100
Subject: Adds the NOT operator

---
 subex/arithmetic.go | 24 ++++++++++++++++++++++++
 subex/parse.go      |  2 ++
 subex/subexast.go   | 15 +++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/subex/arithmetic.go b/subex/arithmetic.go
index 4404a1c..52f576d 100644
--- a/subex/arithmetic.go
+++ b/subex/arithmetic.go
@@ -152,3 +152,27 @@ func reciprocalValues(atoms []walk.Atom) ([]walk.Atom, error) {
 	}
 	return reciprocals, nil
 }
+
+// If all are castable to booleans, NOTs all and returns them
+// Else errors
+func notValues(atoms []walk.Atom) (notted []walk.Atom, err error) {
+	values, err := walk.MemoryCompound(atoms)
+	if err != nil {
+		return nil, err
+	}
+	for _, value := range values {
+		switch v := value.(type) {
+			case walk.ValueNull:
+				notted = append(notted, walk.ValueBool(true))
+			case walk.ValueBool:
+				notted = append(notted, walk.ValueBool(!v))
+			case walk.ValueNumber:
+				notted = append(notted, walk.ValueBool(v == 0))
+			case walk.ValueString:
+				notted = append(notted, walk.ValueBool(len(v) == 0))
+			default:
+				return nil, errors.New("Tried to NOT non-boolean")
+		}
+	}
+	return notted, nil
+}
diff --git a/subex/parse.go b/subex/parse.go
index f5316c9..8b3a553 100644
--- a/subex/parse.go
+++ b/subex/parse.go
@@ -242,6 +242,8 @@ func parseSubex(l *RuneReader, minPower int) SubexAST {
 				lhs = SubexASTNegate {lhs}
 			case r == '/' && minPower <= 8:
 				lhs = SubexASTReciprocal {lhs}
+			case r == '!' && minPower <= 8:
+				lhs = SubexASTNot {lhs}
 			case r == '$' && minPower <= 8:
 				slot := l.next()
 				if slot == eof {
diff --git a/subex/subexast.go b/subex/subexast.go
index 78c9aff..fb16658 100644
--- a/subex/subexast.go
+++ b/subex/subexast.go
@@ -238,3 +238,18 @@ func (ast SubexASTReciprocal) compileWith(next SubexState) SubexState {
 		}),
 	}
 }
+
+// Runs the content Subex and collects the output
+// Maps over the values in the output, casting each to a boolean, notting each and then outputs them
+// Rejects if it cannot cast to boolean
+type SubexASTNot struct {
+	content SubexAST
+}
+func (ast SubexASTNot) compileWith(next SubexState) SubexState {
+	return &SubexCaptureBeginState {
+		next: ast.content.compileWith(&SubexArithmeticEndState {
+			next: next,
+			calculate: notValues,
+		}),
+	}
+}
-- 
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