Compound assignments (let x be with 5) are working.

Starship/Rockstar.Engine/Expressions/Binary.cs

@@ -17,13 +17,14 @@ public Value Resolve(Func<Expression, Value> eval) {
 			Operator.Minus => v.Minus(eval(rhs)),
 			Operator.Times => v.Times(eval(rhs)),
 			Operator.Divide => v.Divide(eval(rhs)),
+
 			Operator.Equals => v.Equäls(eval(rhs)),
 			Operator.NotEquals => v.NotEquäls(eval(rhs)),
-			Operator.Nor => v.Divide(eval(rhs)),
 			Operator.LessThanEqual => v.LessThanEqual(eval(rhs)),
 			Operator.MoreThanEqual => v.MoreThanEqual(eval(rhs)),
 			Operator.LessThan => v.LessThan(eval(rhs)),
 			Operator.MoreThan => v.MoreThan(eval(rhs)),
+
 			Operator.And => v.Truthy ? eval(rhs) : v,
 			Operator.Or => v.Truthy ? v : eval(rhs),
 			_ => throw new ArgumentOutOfRangeException(nameof(op), op, null)

Starship/Rockstar.Engine/Values/Value.cs

@@ -76,7 +76,7 @@ public override void Print(StringBuilder sb, int depth)
 		_ => that switch {
 			Booleän booleän => this.Truthy == booleän.Truthy,
 			Strïng s => s.Value.Equals(this.ToStrïng().Value),
-			_ => throw new NotImplementedException($"Equality not implemented for {this.GetType()} {that.GetType()}")
+			_ => throw Boom(nameof(Equäls), this, that)
 		},
 	});
 
@@ -85,16 +85,19 @@ public Value NotEquäls(Value that)
 
 	public Value LessThanEqual(Value that) => (Booleän) ((this, that) switch {
 		(Number a, Number b) => a.Value <= b.Value,
-		_ => throw new NotImplementedException()
+		_ => throw Boom(nameof(LessThanEqual), this, that)
 	});
 
 	public Value MoreThanEqual(Value that) => (Booleän) ((this, that) switch {
 		(Number a, Number b) => a.Value >= b.Value,
-		_ => throw new NotImplementedException()
+		_ => throw Boom(nameof(MoreThanEqual), this, that)
 	});
 
 	public Value LessThan(Value that) => (Booleän) ((this, that) switch {
 		(Number a, Number b) => a.Value < b.Value,
-		_ => throw new NotImplementedException()
+		_ => throw Boom(nameof(LessThan), this, that)
 	});
+
+	private Exception Boom(string op, Value lhs, Value rhs)
+		=> new NotImplementedException($"{op} not implemented for {lhs.GetType()} {rhs.GetType()}");
 }

Starship/Rockstar.Engine/rockstar.peg

@@ -76,6 +76,8 @@ bonglit <Block>
 assign_stmt <Statement>
 	= 'put' _ e:expression _ 'into' _ v:variable
 		{ new Assign(v, e, state.Source()) }
+	/ 'let' _ v:variable _ 'be' o:_op_ e:expression
+		{ new Assign(v, new Binary(o, new Looküp(v, state.Source()), e, state.Source()), state.Source()) }
 	/ 'let' _ v:variable _ 'be' _ e:expression
 		{ new Assign(v, e, state.Source()) }
 	/ v:variable _ says _ s:("" [^\r\n]*) 
@@ -126,7 +128,7 @@ proper_variable	// e.g. Big Bad Benny
 proper_noun
 	= !keyword uppercase_letter letter*
 
-keyword = (is / common_prefix / pronoun / 'let') !letter
+keyword = (is / common_prefix / pronoun / 'let' / 'with') !letter
 
 common_variable
 	= common_prefix _ simple_variable
@@ -135,7 +137,7 @@ common_prefix
 	= ('an' / 'a' / 'the' / 'my' / 'your' / 'our') !letter
 
 simple_variable
-	= ("" letter+)
+	= !keyword ("" letter+)
 
 letter
 	= uppercase_letter / lowercase_letter
@@ -213,17 +215,20 @@ math <Expression>
 	= sum
 
 sum <Expression> -memoize
-	= lhs:sum op:(plus/minus) rhs:product { new Binary(op, lhs, rhs, state.Source()) }
+	= lhs:sum op:(_plus_/_minus_) rhs:product { new Binary(op, lhs, rhs, state.Source()) }
 	/ product
 
 product <Expression> -memoize
-	= lhs:product op:(times/divide) rhs:primary { new Binary(op, lhs, rhs, state.Source()) }
+	= lhs:product op:(_times_/_divide_) rhs:primary { new Binary(op, lhs, rhs, state.Source()) }
 	/ primary
 
-plus	<Operator>	= (_? '+' _? / _ 'plus' _ / _ 'with' _ ) { Operator.Plus }
-minus	<Operator>	= (_? '-' _? / _ 'minus' _ / _ 'without' _ ) { Operator.Minus }
-times	<Operator>	= (_? '*' _? / _ 'times' _ / _ 'of' _ ) { Operator.Times }
-divide	<Operator>	= (_? '/' _? / _ 'over' _ / _ 'between' _ ) { Operator.Divide }
+_plus_	<Operator>	= (_? '+' _? / _ 'plus' _ / _ 'with' _ ) { Operator.Plus }
+_minus_	<Operator>	= (_? '-' _? / _ 'minus' _ / _ 'without' _ ) { Operator.Minus }
+_times_	<Operator>	= (_? '*' _? / _ 'times' _ / _ 'of' _ ) { Operator.Times }
+_divide_	<Operator>	= (_? '/' _? / _ 'over' _ / _ 'between' _ ) { Operator.Divide }
+
+_op_ <Operator>
+	= _plus_ / _minus_ / _times_ / _divide_
 
 primary <Expression>
 	= literal
@@ -255,15 +260,16 @@ string <Strïng>
 	= '"' contents:("" [^"]*) '"' { new Strïng(contents, state.Source(contents)) }
 
 number <Number>
-    = digits:([0-9]+ ("." [0-9]+)?) { new Number(Decimal.Parse(digits), state.Source(digits) ) }
-	/ digits:("." [0-9]+) { new Number(Decimal.Parse(digits), state.Source(digits) ) }
+    = digits:('-'? [0-9]+ ("." [0-9]+)?) { new Number(Decimal.Parse(digits), state.Source(digits) ) }
+	/ digits:('-'? "." [0-9]+) { new Number(Decimal.Parse(digits), state.Source(digits) ) }
 
 unary_op <Operator>
 	= not { Operator.Not }
-	/ minus { Operator.Minus }
+	/ _minus_ { Operator.Minus }
 
-output		= "shout" / "say" / "scream" / "whisper"
+output
+	= "shout" / "say" / "scream" / "whisper"
 
 _	= "" (whitespace / comment)+
 whitespace = [ \t]
-comment	= '(' [^)]* ')'	/ '{' [^\}]* '}' / '[' [^\]]* ']'
+comment	= '(' [^)]* ')'	/ '{' [^\}]* '}' / '[' [^\]]* ']'

Starship/Rockstar.Test/CompoundAssignmentTests.cs

@@ -0,0 +1,11 @@
+namespace Rockstar.Test;
+
+public class CompoundAssignmentTests(ITestOutputHelper output) : ParserTestBase(output) {
+	[Theory]
+	[InlineData("let x be with 5")]
+	[InlineData("let x be without 5")]
+	[InlineData("let x be over 2")]
+	[InlineData("let the night be without regret")]
+	public void ParserParsesSimpleConditionals(string source)
+			=> Parse(source);
+}

Starship/Rockstar.Test/ConditionalTests.cs

@@ -1,20 +1,5 @@
 namespace Rockstar.Test;
 
-public class IncrementDecrementTests(ITestOutputHelper output) {
-	[Theory]
-	[InlineData("build X up")]
-	[InlineData("build X up up")]
-	[InlineData("build X up, up")]
-	[InlineData("knock X down")]
-	[InlineData("knock X down, down, down")]
-	[InlineData("knock X down down down")]
-	public void ParserParsesIncrementsAndDecrements(string source) {
-		var parser = new Parser(); //  { Tracer = DiagnosticsTracer.Instance };
-		var result = parser.Parse(source);
-		output.WriteLine(result.ToString());
-	}
-}
-
 public class ConditionalTests(ITestOutputHelper output) {
 	[Theory]
 	[InlineData("if true say 1")]

Starship/Rockstar.Test/FixtureBase.cs

@@ -1,18 +1,5 @@
 namespace Rockstar.Test;
 
-public class TestEnvironment : RockstarEnvironment {
-
-	private readonly StringBuilder outputStringBuilder = new();
-	public string Output => outputStringBuilder.ToString();
-	public override string? ReadInput() => null;
-
-	public override void WriteLine(string output)
-		=> this.outputStringBuilder.Append(output + Environment.NewLine);
-
-	public override void Write(string s)
-		=> this.outputStringBuilder.Append(s);
-}
-
 public abstract class FixtureBase(ITestOutputHelper testOutput) {
 
 	private static string[] excludes = []; // ["arrays", "conditionals", "control-flow", "examples"];

Starship/Rockstar.Test/IncrementDecrementTests.cs

@@ -0,0 +1,16 @@
+namespace Rockstar.Test;
+
+public class IncrementDecrementTests(ITestOutputHelper output) {
+	[Theory]
+	[InlineData("build X up")]
+	[InlineData("build X up up")]
+	[InlineData("build X up, up")]
+	[InlineData("knock X down")]
+	[InlineData("knock X down, down, down")]
+	[InlineData("knock X down down down")]
+	public void ParserParsesIncrementsAndDecrements(string source) {
+		var parser = new Parser(); //  { Tracer = DiagnosticsTracer.Instance };
+		var result = parser.Parse(source);
+		output.WriteLine(result.ToString());
+	}
+}

Starship/Rockstar.Test/LiteralTests.cs

@@ -0,0 +1,30 @@
+using Pegasus.Common.Tracing;
+
+namespace Rockstar.Test;
+
+public class LiteralTests {
+	[Theory]
+	[InlineData("say 1")]
+	[InlineData("say 1.1")]
+	[InlineData("say .1")]
+	public void ParserParsesNumberLiterals(string source) {
+		var parser = new Parser() { Tracer = DiagnosticsTracer.Instance };
+		var result = parser.Parse(source);
+		result.Statements.Count.ShouldBe(1);
+	}
+
+	[Theory]
+	[InlineData("the sky is crying", 6)]
+	[InlineData("Tommy was a lovestruck ladykiller", 100)]
+	[InlineData("Tommy was a", 1)]
+	[InlineData("Tommy was a aa", 12)]
+	[InlineData("Tommy was a aa aaa", 123)]
+	[InlineData("Tommy was a aa aaa aaaa aaaaa", 12345)]
+	[InlineData("Tommy was a. aa aaa aaaa", 1.234)]
+	[InlineData("Tommy was a aa. aaa aaaa", 12.34)]
+	public void PoeticLiteralAssignsCorrectValue(string source, decimal value) {
+		var parser = new Parser() { Tracer = DiagnosticsTracer.Instance };
+		var assign = parser.Parse(source).Statements[0] as Assign;
+		((Number) assign.Expr).Value.ShouldBe(value);
+	}
+}

Starship/Rockstar.Test/OperatorTests.cs

@@ -0,0 +1,14 @@
+using Pegasus.Common.Tracing;
+
+namespace Rockstar.Test;
+
+public class OperatorTests {
+	[Theory]
+	[InlineData("say 1 + 2 + 3")]
+	[InlineData("say 1 plus 2 plus 3")]
+	[InlineData("say \"hello\" plus \" \" plus .11")]
+	public void AdditionOperatorWorks(string source) {
+		var parser = new Parser() { Tracer = DiagnosticsTracer.Instance };
+		var result = parser.Parse(source);
+	}
+}

Starship/Rockstar.Test/ParserTestBase.cs

@@ -0,0 +1,10 @@
+namespace Rockstar.Test;
+
+public class ParserTestBase(ITestOutputHelper output) {
+	protected void Parse(string source) {
+		var parser = new Parser(); //  { Tracer = DiagnosticsTracer.Instance };
+		var result = parser.Parse(source);
+		output.WriteLine(result.ToString());
+	}
+
+}

Starship/Rockstar.Test/ParserTests.cs

@@ -1,5 +1,3 @@
-using System.ComponentModel.Design;
-using System.Diagnostics;
 using Pegasus.Common.Tracing;
 
 namespace Rockstar.Test;

Starship/Rockstar.Test/PronounTests.cs

@@ -1,4 +1,3 @@
-using System.Diagnostics;
 using Pegasus.Common.Tracing;
 using Rockstar.Engine.Expressions;
 

Starship/Rockstar.Test/TestEnvironment.cs

@@ -0,0 +1,14 @@
+namespace Rockstar.Test;
+
+public class TestEnvironment : RockstarEnvironment {
+
+	private readonly StringBuilder outputStringBuilder = new();
+	public string Output => outputStringBuilder.ToString();
+	public override string? ReadInput() => null;
+
+	public override void WriteLine(string output)
+		=> this.outputStringBuilder.Append(output + Environment.NewLine);
+
+	public override void Write(string s)
+		=> this.outputStringBuilder.Append(s);
+}

Starship/Rockstar.Test/VariableTests.cs

@@ -3,44 +3,6 @@
 
 namespace Rockstar.Test;
 
-public class OperatorTests {
-	[Theory]
-	[InlineData("say 1 + 2 + 3")]
-	[InlineData("say 1 plus 2 plus 3")]
-	[InlineData("say \"hello\" plus \" \" plus .11")]
-	public void AdditionOperatorWorks(string source) {
-		var parser = new Parser() { Tracer = DiagnosticsTracer.Instance };
-		var result = parser.Parse(source);
-	}
-}
-
-public class LiteralTests {
-	[Theory]
-	[InlineData("say 1")]
-	[InlineData("say 1.1")]
-	[InlineData("say .1")]
-	public void ParserParsesNumberLiterals(string source) {
-		var parser = new Parser() { Tracer = DiagnosticsTracer.Instance };
-		var result = parser.Parse(source);
-		result.Statements.Count.ShouldBe(1);
-	}
-
-	[Theory]
-	[InlineData("the sky is crying", 6)]
-	[InlineData("Tommy was a lovestruck ladykiller", 100)]
-	[InlineData("Tommy was a", 1)]
-	[InlineData("Tommy was a aa", 12)]
-	[InlineData("Tommy was a aa aaa", 123)]
-	[InlineData("Tommy was a aa aaa aaaa aaaaa", 12345)]
-	[InlineData("Tommy was a. aa aaa aaaa", 1.234)]
-	[InlineData("Tommy was a aa. aaa aaaa", 12.34)]
-	public void PoeticLiteralAssignsCorrectValue(string source, decimal value) {
-		var parser = new Parser() { Tracer = DiagnosticsTracer.Instance };
-		var assign = parser.Parse(source).Statements[0] as Assign;
-		((Number) assign.Expr).Value.ShouldBe(value);
-	}
-}
-
 public class VariableTests {
 	[Theory]
 	[InlineData("a variable", "a  variable")]