Add a conversion from our high-level IR to a lower-level one.

src/asts.rs

@@ -1 +1,2 @@
 pub mod hil;
+pub mod lil;

src/asts/hil.rs

@@ -75,12 +75,14 @@ pub enum Expression<Annotation> {
     Primitive(Annotation, Primitive, Vec<Expression<Annotation>>),
 }
 
-#[derive(Clone, Copy, Debug, PartialEq)]
+impl<Annotation: Clone> Expression<Annotation> {
-pub enum Primitive {
+    pub fn annotation(&self) -> Annotation {
-    Plus,
+        match self {
-    Minus,
+            Expression::Value(a, _) => a.clone(),
-    Times,
+            Expression::Reference(a, _) => a.clone(),
-    Divide,
+            Expression::Primitive(a, _, _) => a.clone(),
+        }
+    }
 }
 
 impl<Annotation> Expression<Annotation> {
@@ -116,6 +118,14 @@ impl<Annotation> Expression<Annotation> {
     }
 }
 
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum Primitive {
+    Plus,
+    Minus,
+    Times,
+    Divide,
+}
+
 impl<'a, 'b, D, A> Pretty<'a, D, A> for &'b Primitive
 where
     A: 'a,

src/asts/lil.rs

@@ -0,0 +1,153 @@
+pub use crate::asts::hil::Value;
+use crate::variable_map::{Variable, VariableMap};
+use pretty::{DocAllocator, DocBuilder, Pretty};
+
+pub struct Program<Annotation> {
+    pub statements: Vec<Statement<Annotation>>,
+}
+
+impl<Annotation> Program<Annotation> {
+    pub fn pretty<'a, A, D>(
+        &self,
+        variable_map: &VariableMap,
+        allocator: &'a D,
+    ) -> DocBuilder<'a, D, A>
+    where
+        A: 'a,
+        D: ?Sized + DocAllocator<'a, A>,
+    {
+        let mut result = allocator.nil();
+
+        for stmt in self.statements.iter() {
+            result = result
+                .append(stmt.pretty(variable_map, allocator))
+                .append(allocator.text(";"))
+                .append(allocator.hardline());
+        }
+
+        result
+    }
+}
+
+pub enum Statement<Annotation> {
+    VariableBinding(Annotation, Variable, SimpleExpression<Annotation>),
+    ResultBinding(Annotation, Variable, Primitive<Annotation>),
+    Print(Annotation, Variable),
+}
+
+impl<Annotation> Statement<Annotation> {
+    pub fn pretty<'a, A, D>(
+        &self,
+        variable_map: &VariableMap,
+        allocator: &'a D,
+    ) -> DocBuilder<'a, D, A>
+    where
+        A: 'a,
+        D: ?Sized + DocAllocator<'a, A>,
+    {
+        match self {
+            Statement::VariableBinding(_, var, expr) => {
+                let name = variable_map.get_name(*var).unwrap_or("<unknown>");
+
+                allocator
+                    .text(name.to_string())
+                    .append(allocator.space())
+                    .append(allocator.text("="))
+                    .append(allocator.space())
+                    .append(expr.pretty(variable_map, allocator))
+            }
+
+            Statement::ResultBinding(_, var, prim) => {
+                let name = variable_map.get_name(*var).unwrap_or("<unknown>");
+
+                allocator
+                    .text(name.to_string())
+                    .append(allocator.space())
+                    .append(allocator.text("="))
+                    .append(allocator.space())
+                    .append(prim.pretty(variable_map, allocator))
+            }
+
+            Statement::Print(_, var) => {
+                let name = variable_map.get_name(*var).unwrap_or("<unknown>");
+
+                allocator
+                    .text("print")
+                    .append(allocator.space())
+                    .append(allocator.text(name.to_string()))
+            }
+        }
+    }
+}
+
+pub enum Primitive<Annotation> {
+    Plus(SimpleExpression<Annotation>, SimpleExpression<Annotation>),
+    Minus(SimpleExpression<Annotation>, SimpleExpression<Annotation>),
+    Times(SimpleExpression<Annotation>, SimpleExpression<Annotation>),
+    Divide(SimpleExpression<Annotation>, SimpleExpression<Annotation>),
+}
+
+impl<Annotation> Primitive<Annotation> {
+    pub fn pretty<'a, A, D>(
+        &self,
+        variable_map: &VariableMap,
+        allocator: &'a D,
+    ) -> DocBuilder<'a, D, A>
+    where
+        A: 'a,
+        D: ?Sized + DocAllocator<'a, A>,
+    {
+        match self {
+            Primitive::Plus(a, b) => a
+                .pretty(variable_map, allocator)
+                .append(allocator.space())
+                .append(allocator.text("+"))
+                .append(allocator.space())
+                .append(b.pretty(variable_map, allocator)),
+            Primitive::Minus(a, b) => a
+                .pretty(variable_map, allocator)
+                .append(allocator.space())
+                .append(allocator.text("-"))
+                .append(allocator.space())
+                .append(b.pretty(variable_map, allocator)),
+            Primitive::Times(a, b) => a
+                .pretty(variable_map, allocator)
+                .append(allocator.space())
+                .append(allocator.text("*"))
+                .append(allocator.space())
+                .append(b.pretty(variable_map, allocator)),
+            Primitive::Divide(a, b) => a
+                .pretty(variable_map, allocator)
+                .append(allocator.space())
+                .append(allocator.text("/"))
+                .append(allocator.space())
+                .append(b.pretty(variable_map, allocator)),
+        }
+    }
+}
+
+pub enum SimpleExpression<Annotation> {
+    Reference(Annotation, Variable),
+    Constant(Annotation, Value),
+}
+
+impl<Annotation> SimpleExpression<Annotation> {
+    pub fn pretty<'a, A, D>(
+        &self,
+        variable_map: &VariableMap,
+        allocator: &'a D,
+    ) -> DocBuilder<'a, D, A>
+    where
+        A: 'a,
+        D: ?Sized + DocAllocator<'a, A>,
+    {
+        match self {
+            SimpleExpression::Reference(_, var) => {
+                let name = variable_map.get_name(*var).unwrap_or("<unknown>");
+
+                allocator.text(name.to_string())
+            }
+            SimpleExpression::Constant(_, x) => x.pretty(allocator),
+        }
+    }
+}

src/bin.rs

@@ -3,6 +3,7 @@ use codespan_reporting::diagnostic::Diagnostic;
 use codespan_reporting::files::SimpleFiles;
 use codespan_reporting::term;
 use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
+use ngr::asts::lil;
 use ngr::passes::run_front_end;
 use pretty::Arena;
 
@@ -27,15 +28,29 @@ fn main() {
     let config = codespan_reporting::term::Config::default();
 
     for error in hil_conversion_result.errors.drain(..) {
-        term::emit(&mut writer.lock(), &config, &file_database, &Diagnostic::from(error)).unwrap();
+        term::emit(
+            &mut writer.lock(),
+            &config,
+            &file_database,
+            &Diagnostic::from(error),
+        )
+        .unwrap();
     }
     for warning in hil_conversion_result.warnings.drain(..) {
-        term::emit(&mut writer.lock(), &config, &file_database, &Diagnostic::from(warning)).unwrap();
+        term::emit(
+            &mut writer.lock(),
+            &config,
+            &file_database,
+            &Diagnostic::from(warning),
+        )
+        .unwrap();
     }
 
-    if let Some((tree, variable_map)) = hil_conversion_result.result {
+    if let Some((hil_tree, mut variable_map)) = hil_conversion_result.result {
         let arena = Arena::new();
-        tree.pretty(&variable_map, &arena)
+        let lil_tree = lil::Program::convert(hil_tree, &mut variable_map);
+        lil_tree
+            .pretty(&variable_map, &arena)
             .into_doc()
             .render_colored(72, StandardStream::stdout(ColorChoice::Auto))
             .unwrap()

src/errors.rs

@@ -159,17 +159,15 @@ impl From<Error> for Diagnostic<usize> {
             },
 
             Error::UnboundVariable(location, name) => match location {
-                Location::Manufactured => Diagnostic::error().with_message(format!(
+                Location::Manufactured => {
-                    "Unbound variable '{}'",
+                    Diagnostic::error().with_message(format!("Unbound variable '{}'", name))
-                    name
+                }
-                )),
                 Location::InFile(file_id, offset) => Diagnostic::error()
                     .with_labels(vec![
                         Label::primary(*file_id, *offset..*offset).with_message("unbound here")
                     ])
                     .with_message(format!("Unbound variable '{}'", name)),
-
+            },
-            }
         }
     }
 }

src/passes.rs

@@ -1,12 +1,13 @@
-use codespan_reporting::files::SimpleFiles;
 use crate::asts::hil;
 use crate::errors::Error;
 use crate::syntax;
 use crate::syntax::Location;
 use crate::variable_map::VariableMap;
 use crate::warnings::Warning;
+use codespan_reporting::files::SimpleFiles;
 use std::fs;
 
+mod hil_to_lil;
 mod syntax_to_hil;
 
 pub struct PassResult<T> {
@@ -15,9 +16,9 @@ pub struct PassResult<T> {
     pub errors: Vec<Error>,
 }
 
-impl<T,E> From<E> for PassResult<Option<T>>
+impl<T, E> From<E> for PassResult<Option<T>>
- where
+where
-  Error: From<E>
+    Error: From<E>,
 {
     fn from(x: E) -> Self {
         PassResult {

src/passes/hil_to_lil.rs

@@ -0,0 +1,100 @@
+use crate::asts::hil;
+use crate::asts::lil;
+use crate::variable_map::VariableMap;
+
+impl<Annotation: Clone> lil::Program<Annotation> {
+    pub fn convert(hil_program: hil::Program<Annotation>, variable_map: &mut VariableMap) -> Self {
+        let mut statements = Vec::new();
+
+        for hil_statement in hil_program.statements {
+            statements.append(&mut lil::Statement::convert(hil_statement, variable_map));
+        }
+
+        lil::Program { statements }
+    }
+}
+
+impl<Annotation: Clone> lil::Statement<Annotation> {
+    fn convert(
+        hil_statement: hil::Statement<Annotation>,
+        variable_map: &mut VariableMap,
+    ) -> Vec<Self> {
+        match hil_statement {
+            hil::Statement::Binding(annotation, var, expr) => match expr {
+                hil::Expression::Reference(rhs_annotation, rhs) => {
+                    vec![lil::Statement::VariableBinding(
+                        annotation,
+                        var,
+                        lil::SimpleExpression::Reference(rhs_annotation, rhs),
+                    )]
+                }
+                hil::Expression::Value(rhs_annotation, rhs) => {
+                    vec![lil::Statement::VariableBinding(
+                        annotation,
+                        var,
+                        lil::SimpleExpression::Constant(rhs_annotation, rhs),
+                    )]
+                }
+                hil::Expression::Primitive(_, prim, exprs) => {
+                    let mut result = Vec::new();
+                    let mut arguments = Vec::new();
+
+                    for expr in exprs {
+                        let new_binding = variable_map.gensym();
+                        let expr_ann = expr.annotation();
+                        let temporary_statement =
+                            hil::Statement::Binding(expr_ann.clone(), new_binding, expr);
+                        result.append(&mut lil::Statement::convert(
+                            temporary_statement,
+                            variable_map,
+                        ));
+                        arguments.push(lil::SimpleExpression::Reference(expr_ann, new_binding));
+                    }
+
+                    let final_statement = match prim {
+                        hil::Primitive::Plus => {
+                            let arg1 = arguments.pop().unwrap();
+                            let arg0 = arguments.pop().unwrap();
+                            lil::Statement::ResultBinding(
+                                annotation,
+                                var,
+                                lil::Primitive::Plus(arg0, arg1),
+                            )
+                        }
+                        hil::Primitive::Minus => {
+                            let arg1 = arguments.pop().unwrap();
+                            let arg0 = arguments.pop().unwrap();
+                            lil::Statement::ResultBinding(
+                                annotation,
+                                var,
+                                lil::Primitive::Plus(arg0, arg1),
+                            )
+                        }
+                        hil::Primitive::Times => {
+                            let arg1 = arguments.pop().unwrap();
+                            let arg0 = arguments.pop().unwrap();
+                            lil::Statement::ResultBinding(
+                                annotation,
+                                var,
+                                lil::Primitive::Plus(arg0, arg1),
+                            )
+                        }
+                        hil::Primitive::Divide => {
+                            let arg1 = arguments.pop().unwrap();
+                            let arg0 = arguments.pop().unwrap();
+                            lil::Statement::ResultBinding(
+                                annotation,
+                                var,
+                                lil::Primitive::Plus(arg0, arg1),
+                            )
+                        }
+                    };
+
+                    result.push(final_statement);
+                    result
+                }
+            },
+            hil::Statement::Print(annotation, var) => vec![lil::Statement::Print(annotation, var)],
+        }
+    }
+}

src/passes/syntax_to_hil.rs

@@ -44,7 +44,11 @@ impl hil::Statement<Location> {
 
                 if let Some(var) = var_map.get_variable(&variable_name) {
                     if let Some(orig_loc) = var_map.get_binding_site(var) {
-                        warnings.push(Warning::ShadowedVariable(orig_loc, loc.clone(), variable_name.clone()));
+                        warnings.push(Warning::ShadowedVariable(
+                            orig_loc,
+                            loc.clone(),
+                            variable_name.clone(),
+                        ));
                     } else {
                         errors.push(Error::BindingSiteFailure(
                             loc.clone(),
@@ -65,7 +69,8 @@ impl hil::Statement<Location> {
                 }
             }
 
-            syntax::Statement::Print(variable_loc, variable_name) => match var_map.get_variable(&variable_name) {
+            syntax::Statement::Print(variable_loc, variable_name) => {
+                match var_map.get_variable(&variable_name) {
                     None => PassResult {
                         result: hil::Statement::Print(Location::Manufactured, 0),
                         warnings: vec![],
@@ -80,6 +85,7 @@ impl hil::Statement<Location> {
                 }
             }
         }
+    }
 }
 
 impl hil::Expression<Location> {
@@ -106,7 +112,7 @@ impl hil::Expression<Location> {
                     warnings: vec![],
                     errors: vec![],
                 },
-            }
+            },
 
             syntax::Expression::Primitive(location, name, mut exprs) => {
                 let mut args = vec![];
@@ -145,8 +151,7 @@ impl hil::Expression<Location> {
 impl From<syntax::Value> for hil::Value {
     fn from(x: syntax::Value) -> hil::Value {
         match x {
-            syntax::Value::Number(base, value) =>
+            syntax::Value::Number(base, value) => hil::Value::Number(base, value),
-                hil::Value::Number(base, value),
         }
     }
 }

src/variable_map.rs

@@ -54,4 +54,16 @@ impl VariableMap {
         }
         None
     }
+
+    pub fn gensym(&mut self) -> Variable {
+        let result = self.next_index;
+
+        self.next_index += 1;
+        self.map.insert(
+            result,
+            VariableInfo::new(format!("<x:{}>", result), Location::Manufactured),
+        );
+
+        result
+    }
 }