Sketching July 2025.

sketching/july_2025/closure.dm

@@ -0,0 +1,22 @@
+fn main()
+    var x = 42
+    let cl = { i: Int ->
+        let result = x + i
+        x += 1
+        result
+    }
+    println cl(0) // 42
+    println cl(0) // 43
+    println cl(0) // 44
+end
+
+fn main()
+    var x = 42
+    fn cl(i: Int): Int
+        let result = x + 1
+        x += 1
+        result
+    end
+    println cl(0) // 42
+    println cl(1) // 42
+end

sketching/july_2025/hkt.dm

@@ -0,0 +1,32 @@
+pub hkt Functor[Self<T>]
+    fn <U> map(f: fn (t: T) -> U) -> Self<U>
+end
+
+pub int Iterable<T>
+    fn iter() -> Iterator<T>
+end
+
+pub int Iterator<T> = () -> Option<T>
+
+pub enum Option<T> : Functor[Self<T>]
+    Some(T),
+    None;
+
+    fn unwrap() -> T
+        self is Some(t) ? t : throw Exception('Empty Option')
+    end
+
+    fn expect(msg: String) -> T
+        self is Some(t) ? t : throw Exception(msg)
+    end
+
+    impl Functor
+        fn <U> map(f: fn (t: T) -> U) -> Self<U>
+            self is Some(t) ? Some(f(t)) : None
+        end
+    end
+
+    static fn lift(t: T) -> Self<T>
+        Some(t)
+    end
+end

sketching/july_2025/int.dm

@@ -0,0 +1,14 @@
+int Greeter
+    fn greet(): Void
+end
+
+class MyGreeter(greeting: String) : Greeter
+    impl fn greet()
+        println greeting
+    end
+end
+
+fn main()
+    let g: Greeter = MyGreeter("Hello, World!")
+    g.greet()
+end

sketching/july_2025/name_one.dm

@@ -0,0 +1,39 @@
+fn main(args: Array<String>)
+    if args[0] == 'greet' then
+        println 'Hello!'
+    end
+end
+
+fn main(args: Array<String>)
+    args.each { println it }
+end
+
+fn main(args: Array<String>)
+    if args.find { it == 'greet' } then
+        println 'There was a greet arg'
+    end
+end
+
+// longer
+fn main(args: Array<String>)
+    let findIndexResult: Option<Int> = args.findIndex { it == 'greet' }
+    if findIndexResult.isSome() then
+        let index: Int = findIndex.unwrap()
+        println "greet arg was index ${index}"
+    end
+end
+
+// shorter with destructuring
+fn main(args: Array<String>)
+    if let Some(greetIndex) = args.findIndex { it == 'greet' } then
+        println "greet arg was index ${greetIndex}"
+    end
+end
+
+fn main(args: Array<String>)
+    let parsed: CliArgs = std::cli::parse(args)
+    let greetingCount = parsed.get::<Int>('--count', '-c').orElse(1)
+    if let Some(greeting) = parsed.get('greeting', 'g') then
+        greetingCount.times { println greeting }
+    end
+end

sketching/july_2025/string.dm

@@ -0,0 +1,105 @@
+pub int Display
+    fn toString() -> String
+end
+
+pub int LazyDisplay
+    fn toLazyString() -> DString
+end
+
+pub int DString : Display
+    parts: Array<DStringPart>
+end
+
+pub enum DStringPart
+    Constant(String),
+    Display(Display),
+    Lazy(Fn<Display>)
+end
+
+#internal
+class DStringImpl(parts) : DString
+    cachedEval: Option<String>
+    canCache: Option<Boolean>
+
+    fn getCanCache() -> Boolean
+        for part in parts do
+            if part is Lazy then return false end
+        end
+        true
+    end
+
+    impl Display
+        pub fn toString() -> String
+            if cachedEval is Some(s) then
+                return s
+            end
+            if canCache is None then
+                canCache = Some(getCanCache())
+            end
+            // Note the groovy-like property getter
+            if canCache.truthy then
+                cachedEval = Some(
+                    parts.reduce('') { acc, part ->
+                        let partAsString = match part as
+                            Constant(s) => s,
+                            Display(d) => d.toString(),
+                            Lazy(f) => throw DumbProgrammerException(
+                                'Cannot cache when parts contains a Lazy.'
+                            )
+                        end
+                        acc + partAsString
+                    }
+                )
+                cachedEval.unwrap()
+            else
+                parts.reduce('') { acc, part ->
+                    let partAsString = match part as
+                        Constant(s) => s,
+                        Display(d) => d.toString(),
+                        Lazy(f) => f().toString()
+                    end
+                    acc + partAsString
+                }
+            end
+        end
+    end
+end
+
+// Special "extension" implementation of Option for all T where T : Boolean
+pub int HasTruth
+    fn isTruthy() -> Boolean
+end
+
+impl HasTruth for Option<T> where T is Boolean
+    pub fn isTruthy() -> Boolean
+        self is Some(b) ? b : false
+    end
+end
+
+// some other file
+use std::extensions::HasTruth[Option<Boolean>]
+
+fn maybeSomeOrNone -> Option<Boolean>
+    Some(true)
+end
+
+fn main()
+    let o = maybeSomeOrNone()
+    if o.truthy then
+        println "It's truthy!"
+    else
+        println "It's falsy..."
+    end
+end
+
+fn stringDemo() -> Void
+    let plain = 'Hello, World!'
+    let x = 42
+    let withDisplay = "Hello! x is $x"
+    let withLazy = "Hello! x is ${ x + 42 }"
+    println plain // Hello, World!
+    println withDisplay // Hello! x is 42
+    println withLazy // Hello! x is 84
+    x += 42
+    println withLazy // Hello! x is 126
+end

sketching/july_2025/trait.dm

@@ -0,0 +1,41 @@
+pub trait HasTruth
+    fn isTruthy() -> Boolean
+
+    def fn isFalsy() -> Boolean = !self.truthy
+end
+
+pub trait Functor[Self<T>]
+    fn <U> map(f: fn (t: T) -> U) -> Self<U>
+end
+
+pub trait Lift[Self<T>]
+    static fn lift(t: T) -> Self<T>
+end
+
+pub trait Applicative[Self<T>, U, V] : Functor[Self] + Lift[Self] where T is fn (u: U) -> V
+    fn apply(us: Self<U>) -> Self<V>
+end
+
+pub trait Monad[Self<T>] : Functor[Self] + Lift[Self]
+    fn <U> flatMap(f: fn (t: T) -> Self<U>) -> Self<U>
+end
+
+// Traits as higher-kinded types
+// - Cannot be used as concrete types, casted, etc.
+// - Cannot be constructed/instantiated
+// - Imports are different:
+//   ```
+//   use std::core::Option
+//   use std::trait::Monad[Option<*>] // bring in Monad for all Option<*>
+//   ```
+// - Once imported, fns are in scope
+// - Can also be looked-up 'dictionary' style:
+//   ```
+//   use std::trait::HasTruth[Option<Boolean>]
+//
+//   fn main()
+//     let maybeTruthy: Option<Boolean> = someOtherApiCall()
+//     if HasTruth[maybeTruthy].isTruthy() then
+//       println "It's truthy."
+//     end
+//   ```

src/ast/build.rs

@@ -427,29 +427,37 @@ fn build_namespace(file_id: usize, namespace_pair: Pair<Rule>) -> FullyQualified
 
 fn build_use_statement(file_id: usize, use_statement_pair: Pair<Rule>) -> UseStatement {
     let as_span = use_statement_pair.as_span();
+    let range = Range {
+        start: as_span.start(),
+        end: as_span.end(),
+    };
+
     let mut inner = use_statement_pair.into_inner();
     let inner_length = inner.len();
 
     inner.next().unwrap(); // use
 
-    let mut identifiers = vec![];
-    let mut last = None;
+    let mut prefixes = vec![];
+    let mut built: Option<UseStatement> = None;
 
     for (i, inner_pair) in inner.into_iter().enumerate() {
         if i != inner_length - 2 {
-            identifiers.push(Box::new(expect_and_use(
+            prefixes.push(inner_pair.as_str());
+        } else {
+            built = Some(match inner_pair.as_rule() {
+                Rule::Identifier => UseStatement::Concrete(ConcreteUseStatement::new(
+                    prefixes.iter().map(|s| s.to_string()).collect(),
+                    vec![Box::new(expect_and_use(
                         file_id,
                         inner_pair,
                         Rule::Identifier,
                         build_identifier,
-            )));
-        } else {
-            last = Some(Box::new(match inner_pair.as_rule() {
-                Rule::Identifier => {
-                    UseStatementLast::Identifier(Box::new(build_identifier(file_id, inner_pair)))
-                }
-                Rule::Star => UseStatementLast::Star,
-                Rule::UseList => UseStatementLast::Identifiers(
+                    ))],
+                    file_id,
+                    range,
+                )),
+                Rule::UseList => UseStatement::Concrete(ConcreteUseStatement::new(
+                    prefixes.iter().map(|s| s.to_string()).collect(),
                     inner_pair
                         .into_inner()
                         .map(|identifier_pair| {
@@ -461,21 +469,20 @@ fn build_use_statement(file_id: usize, use_statement_pair: Pair<Rule>) -> UseSta
                             ))
                         })
                         .collect(),
-                ),
+                    file_id,
+                    range,
+                )),
+                Rule::Star => UseStatement::Star(StarUseStatement::new(
+                    prefixes.iter().map(|s| s.to_string()).collect(),
+                    file_id,
+                    range,
+                )),
                 _ => unreachable!(),
-            }));
+            });
         }
     }
 
-    UseStatement::new(
-        identifiers,
-        last.unwrap(),
-        file_id,
-        Range {
-            start: as_span.start(),
-            end: as_span.end(),
-        },
-    )
+    built.unwrap()
 }
 
 fn build_module_level_declaration(file_id: usize, pair: Pair<Rule>) -> ModuleLevelDeclaration {

src/ast/children.rs

@@ -319,21 +319,14 @@ impl NodeInner for CompilationUnit {
 impl NodeInner for UseStatement {
     fn children(&self) -> Vec<NodeRef> {
         let mut children = vec![];
-        children.extend(
-            self.identifiers()
+        match self {
+            UseStatement::Concrete(concrete_use_statement) => children.extend(
+                concrete_use_statement
+                    .identifiers()
                     .iter()
-                .map(|identifier| NodeRef::Identifier(*identifier)),
-        );
-        match self.last() {
-            UseStatementLast::Identifier(identifier) => {
-                children.push(NodeRef::Identifier(identifier))
-            }
-            UseStatementLast::Identifiers(identifiers) => children.extend(
-                identifiers
-                    .iter()
-                    .map(|identifier| NodeRef::Identifier(identifier.clone())),
+                    .map(|identifier| NodeRef::Identifier(*identifier))
             ),
-            UseStatementLast::Star => {}
+            UseStatement::Star(_) => {}
         }
         children
     }

src/ast/node/use_statement.rs

@@ -1,75 +1,48 @@
 use crate::ast::node::named::Named;
 use crate::ast::node::names::Identifier;
-use std::borrow::Cow;
 use std::range::Range;
 
 #[derive(Debug)]
-pub struct UseStatement {
+pub enum UseStatement {
+    Concrete(ConcreteUseStatement),
+    Star(StarUseStatement),
+}
+
+#[derive(Debug)]
+pub struct ConcreteUseStatement {
+    prefixes: Vec<String>,
     identifiers: Vec<Box<Identifier>>,
-    last: Box<UseStatementLast>,
     file_id: usize,
     range: Range<usize>,
 }
 
-impl UseStatement {
+impl ConcreteUseStatement {
     pub fn new(
+        prefixes: Vec<String>,
         identifiers: Vec<Box<Identifier>>,
-        last: Box<UseStatementLast>,
         file_id: usize,
         range: Range<usize>,
     ) -> Self {
-        UseStatement {
+        ConcreteUseStatement {
+            prefixes,
             identifiers,
-            last,
             file_id,
             range,
         }
     }
 
-    pub fn base_name(&self) -> Cow<'_, str> {
-        use UseStatementLast::*;
-        if self.identifiers.is_empty() {
-            match self.last.as_ref() {
-                Identifier(_) => Cow::from(""),
-                Star | Identifiers(_) => panic!(), // should never get here because of grammar
-            }
-        } else if self.identifiers.len() == 1 {
-            self.identifiers[0].name()
-        } else {
-            let mut acc = String::new();
-            for (i, identifier) in self.identifiers.iter().enumerate() {
-                acc.push_str(&identifier.name());
-                if i != self.identifiers.len() - 1 {
-                    acc.push_str("::");
-                }
-            }
-            Cow::from(acc)
-        }
+    pub fn prefixes(&self) -> &Vec<String> {
+        &self.prefixes
     }
 
-    pub fn is_star(&self) -> bool {
-        match self.last.as_ref() {
-            UseStatementLast::Star => true,
-            _ => false,
-        }
+    pub fn join_prefixes(&self) -> String {
+        self.prefixes.join("::")
     }
 
     pub fn identifiers(&self) -> Vec<&Identifier> {
         self.identifiers.iter().map(Box::as_ref).collect()
     }
 
-    pub fn identifiers_mut(&mut self) -> Vec<&mut Identifier> {
-        self.identifiers.iter_mut().map(Box::as_mut).collect()
-    }
-
-    pub fn last(&self) -> &UseStatementLast {
-        &self.last
-    }
-
-    pub fn last_mut(&mut self) -> &mut UseStatementLast {
-        &mut self.last
-    }
-
     pub fn file_id(&self) -> usize {
         self.file_id
     }
@@ -80,8 +53,34 @@ impl UseStatement {
 }
 
 #[derive(Debug)]
-pub enum UseStatementLast {
-    Identifier(Box<Identifier>),
-    Identifiers(Vec<Box<Identifier>>),
-    Star,
+pub struct StarUseStatement {
+    prefixes: Vec<String>,
+    file_id: usize,
+    range: Range<usize>,
+}
+
+impl StarUseStatement {
+    pub fn new(prefixes: Vec<String>, file_id: usize, range: Range<usize>) -> Self {
+        Self {
+            prefixes,
+            file_id,
+            range,
+        }
+    }
+
+    pub fn prefixes(&self) -> &Vec<String> {
+        &self.prefixes
+    }
+
+    pub fn join_prefixes(&self) -> String {
+        self.prefixes.join("::")
+    }
+
+    pub fn file_id(&self) -> usize {
+        self.file_id
+    }
+
+    pub fn range(&self) -> Range<usize> {
+        self.range
+    }
 }

src/ast/pretty_print.rs

@@ -320,6 +320,28 @@ impl PrettyPrint for CompilationUnit {
     }
 }
 
+impl PrettyPrint for UseStatement {
+    fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
+        writer.writeln_indented("UseStatement")?;
+        writer.increase_indent();
+        match self {
+            UseStatement::Concrete(concrete_use_statement) => {
+                writer.writeln_indented(&format!("ConcreteUseStatement(prefixes = {})", concrete_use_statement.join_prefixes()))?;
+                writer.increase_indent();
+                for identifier in concrete_use_statement.identifiers() {
+                    identifier.pretty_print(writer)?;
+                }
+                writer.decrease_indent();
+            }
+            UseStatement::Star(star_use_statement) => {
+                writer.writeln_indented(&format!("StarUseStatement(prefixes = {})", star_use_statement.join_prefixes()))?;
+            }
+        }
+        writer.decrease_indent();
+        Ok(())
+    }
+}
+
 impl PrettyPrint for ModuleLevelDeclaration {
     fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
         use crate::ast::node::level::ModuleLevelDeclaration::*;
@@ -618,39 +640,6 @@ impl PrettyPrint for FieldDeclaration {
     }
 }
 
-impl PrettyPrint for UseStatement {
-    fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
-        writer.writeln_indented("UseStatement")?;
-        writer.increase_indent();
-        for identifier in self.identifiers() {
-            identifier.pretty_print(writer)?;
-        }
-        self.last().pretty_print(writer)?;
-        writer.decrease_indent();
-        Ok(())
-    }
-}
-
-impl PrettyPrint for UseStatementLast {
-    fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
-        writer.writeln_indented("UseStatementLast")?;
-        writer.increase_indent();
-        match self {
-            UseStatementLast::Identifier(i) => i.pretty_print(writer)?,
-            UseStatementLast::Identifiers(is) => {
-                for i in is {
-                    i.pretty_print(writer)?;
-                }
-            }
-            UseStatementLast::Star => {
-                writer.writeln_indented("Star")?;
-            }
-        }
-        writer.decrease_indent();
-        Ok(())
-    }
-}
-
 impl PrettyPrint for BlockStatement {
     fn pretty_print(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
         writer.writeln_indented("BlockStatement")?;

src/ast/unparse.rs

@@ -410,23 +410,13 @@ impl Unparse for CompilationUnit {
 impl Unparse for UseStatement {
     fn unparse(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
         writer.write_indented("use ")?;
-        for (i, identifier) in self.identifiers().iter().enumerate() {
-            identifier.unparse(writer)?;
-            if i != self.identifiers().len() - 2 {
-                // 2 because of use
-                writer.write("::")?;
-            }
-        }
-        self.last().unparse(writer)?;
-        Ok(())
-    }
-}
-
-impl Unparse for UseStatementLast {
-    fn unparse(&self, writer: &mut IndentWriter) -> std::io::Result<()> {
         match self {
-            UseStatementLast::Star => writer.write("*"),
-            UseStatementLast::Identifiers(identifiers) => {
+            UseStatement::Concrete(concrete_use_statement) => {
+                writer.write(&format!("{}::", concrete_use_statement.join_prefixes()))?;
+                let identifiers = concrete_use_statement.identifiers();
+                if identifiers.len() == 1 {
+                    identifiers[0].unparse(writer)?;
+                } else {
                     writer.write("{")?;
                     for (i, identifier) in identifiers.iter().enumerate() {
                         identifier.unparse(writer)?;
@@ -435,11 +425,14 @@ impl Unparse for UseStatementLast {
                         }
                     }
                     writer.write("}")?;
+                }
+            },
+            UseStatement::Star(star_use_statement) => {
+                writer.write(&format!("{}::*", star_use_statement.join_prefixes()))?;
+            }
+        }
         Ok(())
     }
-            UseStatementLast::Identifier(i) => i.unparse(writer),
-        }
-    }
 }
 
 /* Declarations allowed in each level */

src/name_analysis/gather.rs

@@ -364,21 +364,7 @@ fn gather_use_statement(
     fqn_context: &mut FqnContext,
     diagnostics: &mut Vec<DmDiagnostic>,
 ) {
-    if use_statement.is_star() {
     todo!()
-    }
-    let base_name = use_statement.base_name().to_string();
-    match use_statement.last_mut() {
-        UseStatementLast::Identifier(identifier) => {
-            handle_use_statement_import(symbol_table, &base_name, identifier, diagnostics)
-        }
-        UseStatementLast::Identifiers(identifiers) => {
-            for identifier in identifiers {
-                handle_use_statement_import(symbol_table, &base_name, identifier, diagnostics)
-            }
-        }
-        UseStatementLast::Star => panic!(),
-    }
 }
 
 /* Declarations allowed in each level */

src/name_analysis/mod.rs

@@ -56,7 +56,6 @@ mod tests {
     use super::*;
     use crate::ast::build::build_ast;
     use crate::ast::children::NodeRef;
-    use crate::ast::node::use_statement::UseStatementLast;
     use crate::ast::walk::walk_depth_first;
     use crate::parser::{DeimosParser, Rule};
     use crate::std_core::add_std_core_symbols;
@@ -126,25 +125,7 @@ mod tests {
                     panic!("{:?} does not have a saved symbol.", fqn)
                 }
             }
-            NodeRef::UseStatement(use_statement) => match use_statement.last() {
-                UseStatementLast::Identifier(identifier) => {
-                    if identifier.saved_symbol().is_none() {
-                        panic!(
-                            "UseStatement {:?} does not have a saved symbol.",
-                            identifier
-                        )
-                    }
-                }
-                UseStatementLast::Identifiers(identifiers) => {
-                    for identifier in identifiers {
-                        if identifier.saved_symbol().is_none() {
-                            panic!(
-                                "UseStatement {:?} does not have a saved symbol.",
-                                identifier
-                            )
-                        }
-                    }
-                }
+            NodeRef::UseStatement(use_statement) => match use_statement {
                 _ => todo!(),
             },
             _ => {}
@@ -153,35 +134,7 @@ mod tests {
 
     fn assert_resolved_symbols(compilation_unit: &CompilationUnit) {
         walk_depth_first(compilation_unit, &mut |node_ref| match node_ref {
-            NodeRef::UseStatement(use_statement) => match use_statement.last() {
-                UseStatementLast::Identifier(identifier) => {
-                    let use_statement_symbol = identifier
-                        .saved_symbol()
-                        .unwrap()
-                        .unwrap_use_statement_symbol();
-                    let borrowed = use_statement_symbol.borrow();
-                    if borrowed.referenced_symbol().is_none() {
-                        panic!(
-                            "{:?} does not have a referenced symbol.",
-                            use_statement_symbol
-                        )
-                    }
-                }
-                UseStatementLast::Identifiers(identifiers) => {
-                    for identifier in identifiers {
-                        let use_statement_symbol = identifier
-                            .saved_symbol()
-                            .unwrap()
-                            .unwrap_use_statement_symbol();
-                        let borrowed = use_statement_symbol.borrow();
-                        if borrowed.referenced_symbol().is_none() {
-                            panic!(
-                                "{:?} does not have a referenced symbol.",
-                                use_statement_symbol
-                            )
-                        }
-                    }
-                }
+            NodeRef::UseStatement(use_statement) => match use_statement {
                 _ => todo!(),
             },
             _ => {}

src/name_analysis/resolve.rs

@@ -260,36 +260,7 @@ fn resolve_use_statement(
     symbol_table: &mut SymbolTable,
     diagnostics: &mut Vec<DmDiagnostic>,
 ) {
-    let file_id = use_statement.file_id();
-    let use_statement_range = use_statement.range();
-    let base_name = use_statement.base_name().to_string();
-
-    match use_statement.last_mut() {
-        UseStatementLast::Identifier(identifier) => {
-            handle_use_statement_identifier(
-                identifier.deref_mut(),
-                &base_name,
-                symbol_table,
-                diagnostics,
-                file_id,
-                use_statement_range,
-            );
-        }
-        UseStatementLast::Identifiers(identifiers) => {
-            for identifier in identifiers {
-                let identifier_range = identifier.range();
-                handle_use_statement_identifier(
-                    identifier.deref_mut(),
-                    &base_name,
-                    symbol_table,
-                    diagnostics,
-                    file_id,
-                    identifier_range,
-                )
-            }
-        }
-        UseStatementLast::Star => todo!("star imports"),
-    }
+    todo!()
 }
 
 /* Declarations allowed in each level */

src/name_analysis/symbol.rs

@@ -29,14 +29,6 @@ impl SourceDefinition {
         }
     }
     
-    #[deprecated(note = "Use identifier instead.")]
-    pub fn from_use_statement(use_statement: &UseStatement) -> Self {
-        SourceDefinition {
-            file_id: use_statement.file_id(),
-            range: use_statement.range(),
-        }
-    }
-
     pub fn file_id(&self) -> usize {
         self.file_id
     }

src/parser/deimos.pest

@@ -333,6 +333,20 @@ Namespace = {
     ~ FullyQualifiedName
 }
 
+UseStatement = {
+      Use
+    ~ Identifier
+    ~ ( "::" ~ Identifier )*
+    ~ ( "::" ~ ( Star | UseList ) )?
+}
+
+UseList = {
+      "{"
+    ~ Identifier
+    ~ ( "," ~ Identifier )*
+    ~ "}"
+}
+
 // Organizational declarations
 
 ModuleLevelDeclaration = {
@@ -523,20 +537,6 @@ Field = {
 
 // Statements
 
-UseStatement = {
-      Use
-    ~ Identifier
-    ~ ( "::" ~ Identifier )*
-    ~ ( "::" ~ ( Star | UseList ) )?
-}
-
-UseList = {
-      "{"
-    ~ Identifier
-    ~ ( "," ~ Identifier )*
-    ~ "}"
-}
-
 BlockStatement = {
       "{"
     ~ Statement*