From dec2d22b80af7299b9b2c8db3970fa49cc7607f8 Mon Sep 17 00:00:00 2001
From: Ross Andrews <ross.andrews@gmail.com>
Date: Tue, 5 Apr 2022 18:05:24 -0500
Subject: [PATCH] WIP, implementing macros

---
 vasm/src/ast.rs            |  69 +++++---
 vasm/src/parse_error.rs    |  10 +-
 vasm/src/vasm.pest         |   6 +-
 vasm/src/vasm_assembler.rs | 326 ++++++++++++++++++++++++++++++-------
 vasm/src/vasm_evaluator.rs | 103 +++++++-----
 vasm/src/vasm_parser.rs    |  77 ++++++---
 6 files changed, 436 insertions(+), 155 deletions(-)

diff --git a/vasm/src/ast.rs b/vasm/src/ast.rs
index 6efd999..e385ee0 100644
--- a/vasm/src/ast.rs
+++ b/vasm/src/ast.rs
@@ -1,5 +1,6 @@
 use vcore::opcodes::Opcode;
 
+use std::collections::BTreeMap;
 use std::fmt::{Display, Formatter};
 
 /// One of the five arithmetical operators
@@ -16,50 +17,80 @@ pub enum Operator {
 /// line offset, or an expr containing a sequence of other Nodes joined by same-precedence
 /// `Operator`s.
 #[derive(Debug, PartialEq, Clone)]
-pub enum Node<'a> {
+pub enum Node {
     Number(i32),
-    Label(&'a str),
-    RelativeLabel(&'a str),
+    Label(String),
+    RelativeLabel(String),
     AbsoluteOffset(i32),
     RelativeOffset(i32),
-    Expr(Box<Node<'a>>, Vec<(Operator, Node<'a>)>),
+    Expr(Box<Node>, Vec<(Operator, Node)>),
 }
 
-#[derive(Debug, PartialEq, Copy, Clone)]
-pub struct Label<'a>(pub &'a str);
+impl Node {
+    pub fn label(lbl: &str) -> Self {
+        Self::Label(lbl.to_string())
+    }
+    pub fn relative_label(lbl: &str) -> Self {
+        Self::RelativeLabel(lbl.to_string())
+    }
+}
 
-impl<'a> Display for Label<'a> {
+#[derive(Debug, PartialEq, Clone)]
+pub struct Label(pub String);
+
+impl Display for Label {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         write!(f, "{}", self.0)
     }
 }
 
-#[derive(Debug, PartialEq, Clone)]
-pub enum VASMLine<'a> {
-    Instruction(Option<Label<'a>>, Opcode, Option<Node<'a>>),
-    Db(Option<Label<'a>>, Node<'a>),
-    StringDb(Option<Label<'a>>, String),
-    Org(Option<Label<'a>>, Node<'a>),
-    Equ(Label<'a>, Node<'a>),
-    LabelDef(Label<'a>),
+impl From<&str> for Label {
+    fn from(s: &str) -> Self {
+        Self(s.to_string())
+    }
 }
 
-impl<'a> VASMLine<'a> {
-    pub fn label(&self) -> Option<Label<'a>> {
+pub type Scope = BTreeMap<String, i32>;
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum Macro {
+    Include(String),
+    If,
+    Unless,
+    Else,
+    While,
+    Until,
+    Do,
+    End,
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum VASMLine {
+    Instruction(Option<Label>, Opcode, Option<Node>),
+    Db(Option<Label>, Node),
+    StringDb(Option<Label>, String),
+    Org(Option<Label>, Node),
+    Equ(Label, Node),
+    LabelDef(Label),
+    Macro(Macro),
+}
+
+impl VASMLine {
+    pub fn label(&self) -> Option<&Label> {
         match self {
             VASMLine::Instruction(Some(lbl), _, _)
             | VASMLine::Db(Some(lbl), _)
             | VASMLine::StringDb(Some(lbl), _)
             | VASMLine::Org(Some(lbl), _)
             | VASMLine::Equ(lbl, _)
-            | VASMLine::LabelDef(lbl) => Some(*lbl),
+            | VASMLine::LabelDef(lbl) => Some(lbl),
             _ => None,
         }
     }
     pub fn zero_length(&self) -> bool {
         matches!(
             self,
-            VASMLine::Org(_, _) | VASMLine::Equ(_, _) | VASMLine::LabelDef(_)
+            VASMLine::Org(_, _) | VASMLine::Equ(_, _) | VASMLine::LabelDef(_) | VASMLine::Macro(_)
         )
     }
 }
diff --git a/vasm/src/parse_error.rs b/vasm/src/parse_error.rs
index 35efdec..99b951b 100644
--- a/vasm/src/parse_error.rs
+++ b/vasm/src/parse_error.rs
@@ -3,18 +3,18 @@ use std::fmt::{Display, Formatter};
 use vcore::opcodes::InvalidMnemonic;
 
 #[derive(Debug, PartialEq, Clone)]
-pub enum ParseError<'a> {
+pub enum ParseError {
     LineParseFailure,
-    InvalidInstruction(&'a str),
+    InvalidInstruction(String),
 }
 
-impl<'a> From<InvalidMnemonic<'a>> for ParseError<'a> {
+impl<'a> From<InvalidMnemonic<'a>> for ParseError {
     fn from(err: InvalidMnemonic<'a>) -> Self {
-        Self::InvalidInstruction(err.0)
+        Self::InvalidInstruction(err.0.into())
     }
 }
 
-impl<'a> Display for ParseError<'a> {
+impl Display for ParseError {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         use ParseError::*;
         match self {
diff --git a/vasm/src/vasm.pest b/vasm/src/vasm.pest
index 2f208bb..71dc13b 100644
--- a/vasm/src/vasm.pest
+++ b/vasm/src/vasm.pest
@@ -68,5 +68,9 @@ db_string = { label_def? ~ ".db" ~ string }
 org_directive = { label_def? ~ ".org" ~ expr }
 equ_directive = { label_def ~ ".equ" ~ expr }
 
+include = { "include" ~ string }
+control = { "if" | "unless" | "while" | "until" | "do" | "else" | "end" }
+preprocessor = {"#" ~ (control | include) }
+
 // Finally the entire pattern for an assembly line:
-line = { SOI ~ (db_word | db_string | org_directive | equ_directive | instruction | label_def) ~ EOI }
\ No newline at end of file
+line = { SOI ~ (preprocessor | db_word | db_string | org_directive | equ_directive | instruction | label_def) ~ EOI }
\ No newline at end of file
diff --git a/vasm/src/vasm_assembler.rs b/vasm/src/vasm_assembler.rs
index 48b4d90..3650984 100644
--- a/vasm/src/vasm_assembler.rs
+++ b/vasm/src/vasm_assembler.rs
@@ -1,21 +1,23 @@
-use crate::ast::{Label, VASMLine};
+use crate::ast::{Label, Macro, Scope, VASMLine};
 use crate::parse_error::ParseError;
-use crate::vasm_evaluator::{eval, EvalError, Scope};
+use crate::vasm_evaluator::{eval, EvalError};
 use crate::vasm_parser::parse_vasm_line;
 use std::collections::BTreeMap;
 use std::fmt::{Display, Formatter};
 
 #[derive(Debug, Clone, PartialEq)]
-pub enum AssembleError<'a> {
-    ParseError(i32, ParseError<'a>),
-    EquResolveError(i32, &'a str, EvalError<'a>),
-    EquDuplicateError(i32, &'a str),
-    OrgResolveError(i32, EvalError<'a>),
-    ArgError(i32, EvalError<'a>),
+pub enum AssembleError {
+    ParseError(usize, ParseError),
+    EquResolveError(usize, String, EvalError),
+    EquDuplicateError(usize, String),
+    OrgResolveError(usize, EvalError),
+    ArgError(usize, EvalError),
     NoCode,
+    IncludeError(usize, String),
+    MacroError(usize),
 }
 
-impl<'a> Display for AssembleError<'a> {
+impl Display for AssembleError {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
             AssembleError::EquResolveError(line, name, err) => {
@@ -36,32 +38,140 @@ impl<'a> Display for AssembleError<'a> {
             AssembleError::ParseError(line, err) => {
                 write!(f, "Parse error on line {}: {}", line, err)
             }
+            AssembleError::IncludeError(line, file) => {
+                write!(f, "Cannot read \"{}\" on line {}", file, line)
+            }
+            AssembleError::MacroError(line) => {
+                write!(f, "Malformed macro control structure on line {}", line)
+            }
         }
     }
 }
 
+#[derive(Debug, Clone, PartialEq)]
+struct Line {
+    line: VASMLine,
+    line_num: usize,
+    file: String,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+enum LoopType {
+    While,
+    Until,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+enum ControlStructure {
+    Target(String),
+    Loop(String, LoopType),
+}
+
+fn preprocess<'a, T, F>(iter: T, filename: String, include: &F) -> Result<Vec<Line>, AssembleError>
+where
+    T: IntoIterator<Item = &'a str>,
+    F: Fn(String) -> Result<T, AssembleError>,
+{
+    let mut current_sym = 0;
+    let mut gensym = || {
+        current_sym += 1;
+        format!("__gensym_{}", current_sym)
+    };
+    let mut all_lines = Vec::new();
+
+    let mut iter_stack = vec![iter.into_iter().enumerate()];
+    let mut filename_stack = vec![filename];
+    let mut control_stack = Vec::new();
+
+    while !iter_stack.is_empty() {
+        if let Some((line_idx, line)) = iter_stack.last_mut().unwrap().next() {
+            match parse_vasm_line(line)
+                .map_err(|err| AssembleError::ParseError(line_idx + 1, err))?
+            {
+                VASMLine::Macro(mac) => match mac {
+                    Macro::Include(file) => {
+                        filename_stack.push(file.clone());
+                        iter_stack.push(include(file)?.into_iter().enumerate());
+                    }
+                    Macro::If => {
+                        let label = gensym();
+                        control_stack.push(ControlStructure::Target(label.clone()));
+                        all_lines.push(Line {
+                            line: parse_vasm_line(format!("brz @{}", label).as_str()).unwrap(),
+                            line_num: line_idx + 1,
+                            file: filename_stack.last().unwrap().clone(),
+                        })
+                    }
+                    Macro::Unless => {
+                        let label = gensym();
+                        control_stack.push(ControlStructure::Target(label.clone()));
+                        all_lines.push(Line {
+                            line: parse_vasm_line(format!("brnz @{}", label).as_str()).unwrap(),
+                            line_num: line_idx + 1,
+                            file: filename_stack.last().unwrap().clone(),
+                        })
+                    }
+                    Macro::Else => {
+                        if let Some(ControlStructure::Target(old_end)) = control_stack.pop() {
+                            let new_end = gensym();
+                            control_stack.push(ControlStructure::Target(new_end.clone()));
+                            all_lines.push(Line {
+                                line: parse_vasm_line(format!("jmpr @{}", new_end).as_str())
+                                    .unwrap(),
+                                line_num: line_idx + 1,
+                                file: filename_stack.last().unwrap().clone(),
+                            });
+                            all_lines.push(Line {
+                                line: VASMLine::LabelDef(Label(old_end)),
+                                line_num: line_idx + 1,
+                                file: filename_stack.last().unwrap().clone(),
+                            })
+                        } else {
+                            return Err(AssembleError::MacroError(line_idx + 1));
+                        }
+                    }
+                    Macro::While => {}
+                    Macro::Until => {}
+                    Macro::Do => {}
+                    Macro::End => {}
+                },
+                normal_line => all_lines.push(Line {
+                    line: normal_line,
+                    line_num: line_idx + 1,
+                    file: filename_stack.last().unwrap().clone(),
+                }),
+            }
+        } else {
+            iter_stack.pop();
+            filename_stack.pop();
+        }
+    }
+
+    Ok(all_lines)
+}
+
 /// This will solve all the .equ directives and return a symbol table of them.
 /// .equ directives must be able to be solved in order, that is, in terms of
 /// only preceding .equ directives. Anything else is an error.
-fn solve_equs<'a>(lines: &Vec<VASMLine<'a>>) -> Result<Scope<'a>, AssembleError<'a>> {
+fn solve_equs(lines: &[VASMLine]) -> Result<Scope, AssembleError> {
     let mut scope: Scope = Scope::new();
-    let line_nums: BTreeMap<i32, i32> = BTreeMap::new();
+    let line_nums: BTreeMap<usize, i32> = BTreeMap::new();
     for (line_idx, line) in lines.iter().enumerate() {
-        let line_num = (line_idx + 1) as i32;
+        let line_num = line_idx + 1;
         if let VASMLine::Equ(Label(name), expr) = line {
-            let value = eval(&expr, line_num as i32, &line_nums, &scope)
-                .map_err(|e| AssembleError::EquResolveError(line_num as i32, name, e))?;
+            let value = eval(expr, line_num, &line_nums, &scope)
+                .map_err(|e| AssembleError::EquResolveError(line_num, name.to_string(), e))?;
 
-            if let Some(_old_value) = scope.insert(name, value) {
-                return Err(AssembleError::EquDuplicateError(line_num as i32, name));
+            if let Some(_old_value) = scope.insert(name.clone(), value) {
+                return Err(AssembleError::EquDuplicateError(line_num, name.to_string()));
             }
         }
     }
     Ok(scope)
 }
 
-type LineLengths = BTreeMap<i32, usize>;
-type LineAddresses = BTreeMap<i32, i32>;
+type LineLengths = BTreeMap<usize, usize>;
+type LineAddresses = BTreeMap<usize, i32>;
 
 fn arg_length(val: i32) -> usize {
     if val < 0 {
@@ -89,17 +199,17 @@ fn arg_length(val: i32) -> usize {
 ///   what we know right now (.equs), are however long that argument is. If we don't
 ///   know right now (based on a label, say) then we'll set aside the full 3 bytes (so it's
 ///   4 bytes long, with the instruction byte).
-fn measure_instructions<'a>(lines: &Vec<VASMLine<'a>>, scope: &Scope) -> LineLengths {
-    let line_nums: BTreeMap<i32, i32> = BTreeMap::new();
+fn measure_instructions(lines: &[VASMLine], scope: &Scope) -> LineLengths {
+    let line_nums: BTreeMap<usize, i32> = BTreeMap::new();
     let mut lengths = LineLengths::new();
     for (line_idx, line) in lines.iter().enumerate() {
-        let line_num = (line_idx + 1) as i32;
+        let line_num = line_idx + 1;
         match line {
             VASMLine::Instruction(_, _, None) => {
                 lengths.insert(line_num, 1);
             }
             VASMLine::Instruction(_, _, Some(node)) => {
-                let len = eval(&node, line_num as i32, &line_nums, scope).map_or(3, arg_length);
+                let len = eval(node, line_num, &line_nums, scope).map_or(3, arg_length);
                 lengths.insert(line_num, len + 1);
             }
             VASMLine::Db(_, _) => {
@@ -111,6 +221,7 @@ fn measure_instructions<'a>(lines: &Vec<VASMLine<'a>>, scope: &Scope) -> LineLen
             VASMLine::Org(_, _) | VASMLine::Equ(_, _) | VASMLine::LabelDef(_) => {
                 lengths.insert(line_num, 0);
             }
+            VASMLine::Macro(_) => unreachable!(),
         }
     }
     lengths
@@ -126,26 +237,26 @@ fn measure_instructions<'a>(lines: &Vec<VASMLine<'a>>, scope: &Scope) -> LineLen
 ///
 /// But, we'll skip labels that come before .equs: that would make every .equ set to its address,
 /// rather than the argument.
-fn place_labels<'a>(
-    lines: &Vec<VASMLine<'a>>,
-    scope: Scope<'a>,
+fn place_labels(
+    lines: &[VASMLine],
+    scope: Scope,
     lengths: &LineLengths,
-) -> Result<(LineAddresses, Scope<'a>), AssembleError<'a>> {
+) -> Result<(LineAddresses, Scope), AssembleError> {
     let mut scope = scope;
     let mut address = 0;
     let mut addresses = LineAddresses::new();
     for (line_idx, line) in lines.iter().enumerate() {
-        let line_num = (line_idx + 1) as i32;
+        let line_num = line_idx + 1;
 
         if let VASMLine::Org(_, expr) = line {
-            address = eval(&expr, line_num, &addresses, &scope)
+            address = eval(expr, line_num, &addresses, &scope)
                 .map_err(|err| AssembleError::OrgResolveError(line_num, err))?;
             addresses.insert(line_num, address);
         }
 
         if let Some(Label(label)) = line.label() {
             if !scope.contains_key(label) {
-                scope.insert(label, address as i32);
+                scope.insert(label.clone(), address as i32);
             }
         }
 
@@ -168,35 +279,33 @@ fn poke_word(code: &mut Vec<u8>, at: usize, word: i32) {
 }
 
 /// Find the lower and upper bounds where this program will place memory
-fn code_bounds<'a>(
-    lines: &Vec<VASMLine<'a>>,
+fn code_bounds(
+    lines: &[VASMLine],
     line_addresses: &LineAddresses,
     line_lengths: &LineLengths,
-) -> Result<(usize, usize), AssembleError<'a>> {
+) -> Result<(usize, usize), AssembleError> {
     let mut actual_lines = lines
         .iter()
         .enumerate()
         .filter(|(_, line)| !line.zero_length());
     let (first_idx, _) = actual_lines.next().ok_or(AssembleError::NoCode)?;
-    let start = line_addresses[&(first_idx as i32 + 1)] as usize;
+    let start = line_addresses[&(first_idx + 1)] as usize;
 
     let actual_lines = lines
         .iter()
         .enumerate()
         .filter(|(_, line)| !line.zero_length());
     let (last_idx, _) = actual_lines.last().unwrap();
-    let end = line_addresses[&(last_idx as i32 + 1)] as usize;
-    let end_length = line_lengths[&(last_idx as i32 + 1)];
+    let end = line_addresses[&(last_idx + 1)] as usize;
+    let end_length = line_lengths[&(last_idx + 1)];
 
     Ok((start, end + end_length - 1))
 }
 
-pub fn assemble<'a, T: IntoIterator<Item = &'a str>>(
-    lines: T,
-) -> Result<Vec<u8>, AssembleError<'a>> {
+pub fn assemble<'a, T: IntoIterator<Item = &'a str>>(lines: T) -> Result<Vec<u8>, AssembleError> {
     let mut parsed = Vec::new();
     for (line_idx, line) in lines.into_iter().enumerate() {
-        let line_num = (line_idx + 1) as i32;
+        let line_num = line_idx + 1;
         parsed.push(parse_vasm_line(line).map_err(|err| AssembleError::ParseError(line_num, err))?)
     }
 
@@ -218,8 +327,8 @@ pub fn assemble<'a, T: IntoIterator<Item = &'a str>>(
 ///
 /// Vulcan is a little-endian architecture: multi-byte arguments / .dbs will store the
 /// least-significant byte at the lowest address, then the more significant bytes following.
-fn generate_code<'a>(lines: Vec<VASMLine<'a>>) -> Result<Vec<u8>, AssembleError<'a>> {
-    let lines: Vec<VASMLine<'a>> = lines.into_iter().collect();
+fn generate_code(lines: Vec<VASMLine>) -> Result<Vec<u8>, AssembleError> {
+    let lines: Vec<VASMLine> = lines.into_iter().collect();
     let scope = solve_equs(&lines)?;
     let line_lengths = measure_instructions(&lines, &scope);
     let (line_addresses, scope) = place_labels(&lines, scope, &line_lengths)?;
@@ -229,7 +338,7 @@ fn generate_code<'a>(lines: Vec<VASMLine<'a>>) -> Result<Vec<u8>, AssembleError<
     let mut current_addr = start;
 
     for (line_idx, line) in lines.iter().enumerate() {
-        let line_num = (line_idx + 1) as i32;
+        let line_num = line_idx + 1;
         match line {
             VASMLine::Instruction(_, opcode, None) => {
                 code[current_addr] = u8::from(*opcode) << 2;
@@ -267,6 +376,7 @@ fn generate_code<'a>(lines: Vec<VASMLine<'a>>) -> Result<Vec<u8>, AssembleError<
                 current_addr = line_addresses[&(line_num + 1)] as usize;
             }
             VASMLine::Equ(_, _) | VASMLine::LabelDef(_) => {}
+            VASMLine::Macro(_) => unreachable!(),
         }
     }
 
@@ -278,11 +388,12 @@ mod test {
     use super::AssembleError::*;
     use super::EvalError::*;
     use super::*;
-    use crate::ast::VASMLine;
+    use crate::ast::{Node, VASMLine};
     use crate::parse_error;
     use crate::vasm_parser::parse_vasm_line;
+    use vcore::opcodes::Opcode;
 
-    fn parse<'a, T: IntoIterator<Item = &'a str>>(lines: T) -> Vec<VASMLine<'a>> {
+    fn parse<'a, T: IntoIterator<Item = &'a str>>(lines: T) -> Vec<VASMLine> {
         lines
             .into_iter()
             .map(|line| parse_vasm_line(line).unwrap())
@@ -291,7 +402,7 @@ mod test {
 
     fn place_labels_pass<'a, T: IntoIterator<Item = &'a str>>(
         lines: T,
-    ) -> Result<(LineAddresses, Scope<'a>), AssembleError<'a>> {
+    ) -> Result<(LineAddresses, Scope), AssembleError> {
         let parsed_lines = parse(lines);
         let scope = solve_equs(&parsed_lines).unwrap();
         let lengths = measure_instructions(&parsed_lines, &scope);
@@ -300,7 +411,7 @@ mod test {
 
     fn bounds<'a, T: IntoIterator<Item = &'a str>>(
         lines: T,
-    ) -> Result<(usize, usize), AssembleError<'a>> {
+    ) -> Result<(usize, usize), AssembleError> {
         let parsed_lines = parse(lines);
         let scope = solve_equs(&parsed_lines).unwrap();
         let lengths = measure_instructions(&parsed_lines, &scope);
@@ -312,19 +423,19 @@ mod test {
     fn test_equs() {
         assert_eq!(
             solve_equs(&parse(["blah: .equ 5+3"])),
-            Ok([("blah", 8)].into())
+            Ok([("blah".to_string(), 8)].into())
         );
         assert_eq!(
             solve_equs(&parse(["blah: .equ 5", "foo: .equ 3"])),
-            Ok([("blah", 5), ("foo", 3)].into())
+            Ok([("blah".to_string(), 5), ("foo".to_string(), 3)].into())
         );
         assert_eq!(
             solve_equs(&parse(["blah: .equ 5", "foo: .equ blah + 7"])),
-            Ok([("blah", 5), ("foo", 12)].into())
+            Ok([("blah".to_string(), 5), ("foo".to_string(), 12)].into())
         );
         assert_eq!(
             solve_equs(&parse(["add", "blah: .equ 5"])),
-            Ok([("blah", 5)].into())
+            Ok([("blah".to_string(), 5)].into())
         );
     }
 
@@ -332,15 +443,23 @@ mod test {
     fn test_unsolvable_equs() {
         assert_eq!(
             solve_equs(&parse(["blah: .equ 5", "foo: .equ banana"])),
-            Err(EquResolveError(2, "foo", MissingLabel("banana")))
+            Err(EquResolveError(
+                2,
+                "foo".into(),
+                MissingLabel("banana".into())
+            ))
         );
         assert_eq!(
             solve_equs(&parse(["blah: .equ foo+3", "foo: .equ 7"])),
-            Err(EquResolveError(1, "blah", MissingLabel("foo")))
+            Err(EquResolveError(
+                1,
+                "blah".into(),
+                MissingLabel("foo".into())
+            ))
         );
         assert_eq!(
             solve_equs(&parse(["blah: .equ 3", "blah: .equ 7"])),
-            Err(EquDuplicateError(2, "blah"))
+            Err(EquDuplicateError(2, "blah".into()))
         );
     }
 
@@ -364,7 +483,7 @@ mod test {
         assert_eq!(
             measure_instructions(
                 &parse(["add 2 + foo", "add 3 + blah", "jmpr @foo"]),
-                &[("blah", 300)].into()
+                &[("blah".to_string(), 300)].into()
             ),
             [(1, 4), (2, 3), (3, 4)].into()
         );
@@ -376,7 +495,7 @@ mod test {
             place_labels_pass(["start: .org 256", "add", "dup"]),
             Ok((
                 [(1, 256), (2, 256), (3, 257)].into(),
-                [("start", 256)].into()
+                [("start".to_string(), 256)].into()
             ))
         );
         assert_eq!(
@@ -387,14 +506,14 @@ mod test {
             place_labels_pass(["start: .equ 256", "blah: .org start + 4", "add"]),
             Ok((
                 [(1, 0), (2, 260), (3, 260)].into(),
-                [("blah", 260), ("start", 256)].into()
+                [("blah".to_string(), 260), ("start".to_string(), 256)].into()
             ))
         );
         assert_eq!(
             place_labels_pass(["start: .org 256", "blah: .org start + 10", "add"]),
             Ok((
                 [(1, 256), (2, 266), (3, 266)].into(),
-                [("blah", 266), ("start", 256)].into()
+                [("blah".to_string(), 266), ("start".to_string(), 256)].into()
             ))
         );
     }
@@ -403,11 +522,11 @@ mod test {
     fn test_unresolvable_orgs() {
         assert_eq!(
             place_labels_pass([".org 0xffffff - blah"]),
-            Err(OrgResolveError(1, EvalError::MissingLabel("blah")))
+            Err(OrgResolveError(1, EvalError::MissingLabel("blah".into())))
         );
         assert_eq!(
             place_labels_pass(["blah: .org blah"]),
-            Err(OrgResolveError(1, EvalError::MissingLabel("blah")))
+            Err(OrgResolveError(1, EvalError::MissingLabel("blah".into())))
         );
     }
 
@@ -455,8 +574,95 @@ mod test {
             assemble(["apple"]),
             Err(ParseError(
                 1,
-                parse_error::ParseError::InvalidInstruction("apple")
+                parse_error::ParseError::InvalidInstruction("apple".into())
             ))
         );
     }
+
+    #[test]
+    fn test_preprocess() {
+        let include = |name: String| Err(AssembleError::IncludeError(1, name));
+        let lines = vec!["add"];
+        assert_eq!(
+            preprocess(lines, "blah".to_string(), &include),
+            Ok(vec![Line {
+                line_num: 1,
+                file: "blah".to_string(),
+                line: VASMLine::Instruction(None, Opcode::Add, None)
+            }])
+        );
+    }
+
+    #[test]
+    fn test_preprocess_include() {
+        let include = |_name: String| Ok(vec!["sub"]);
+        let lines = vec!["#include \"foo\"", "add"];
+        assert_eq!(
+            preprocess(lines, "blah".to_string(), &include),
+            Ok(vec![
+                Line {
+                    line_num: 1,
+                    file: "foo".to_string(),
+                    line: VASMLine::Instruction(None, Opcode::Sub, None)
+                },
+                Line {
+                    line_num: 2,
+                    file: "blah".to_string(),
+                    line: VASMLine::Instruction(None, Opcode::Add, None)
+                }
+            ])
+        );
+    }
+
+    #[test]
+    fn test_preprocess_if() {
+        let include = |_name: String| Ok(vec![]);
+        let lines = vec!["#if"];
+        assert_eq!(
+            preprocess(lines, "blah".to_string(), &include),
+            Ok(vec![Line {
+                line_num: 1,
+                file: "blah".to_string(),
+                line: VASMLine::Instruction(
+                    None,
+                    Opcode::Brz,
+                    Some(Node::relative_label("__gensym_1"))
+                )
+            }])
+        )
+    }
+
+    #[test]
+    fn test_preprocess_else() {
+        let include = |_name: String| Ok(vec![]);
+        let lines = vec!["#if", "#else"];
+        assert_eq!(
+            preprocess(lines, "blah".to_string(), &include),
+            Ok(vec![
+                Line {
+                    line_num: 1,
+                    file: "blah".to_string(),
+                    line: VASMLine::Instruction(
+                        None,
+                        Opcode::Brz,
+                        Some(Node::relative_label("__gensym_1"))
+                    )
+                },
+                Line {
+                    line_num: 2,
+                    file: "blah".to_string(),
+                    line: VASMLine::Instruction(
+                        None,
+                        Opcode::Jmpr,
+                        Some(Node::relative_label("__gensym_2"))
+                    )
+                },
+                Line {
+                    line_num: 2,
+                    file: "blah".to_string(),
+                    line: VASMLine::LabelDef(Label("__gensym_1".to_string()))
+                }
+            ])
+        )
+    }
 }
diff --git a/vasm/src/vasm_evaluator.rs b/vasm/src/vasm_evaluator.rs
index 9b887e3..40e43ee 100644
--- a/vasm/src/vasm_evaluator.rs
+++ b/vasm/src/vasm_evaluator.rs
@@ -1,14 +1,15 @@
-use crate::ast::{Node, Operator};
+use crate::ast::{Node, Operator, Scope};
 use std::collections::BTreeMap;
 use std::fmt::{Display, Formatter};
 
 #[derive(Debug, Clone, PartialEq)]
-pub enum EvalError<'a> {
-    MissingLabel(&'a str),
-    UnknownAddress(i32),
+pub enum EvalError {
+    MissingLabel(String),
+    UnknownAddress(usize),
+    OffsetError(usize, i32),
 }
 
-impl<'a> Display for EvalError<'a> {
+impl Display for EvalError {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
             EvalError::MissingLabel(label) => write!(f, "Unable to resolve label {}", label),
@@ -17,11 +18,20 @@ impl<'a> Display for EvalError<'a> {
                 "Unable to calculate starting address of line {}",
                 line_num
             ),
+            EvalError::OffsetError(line_num, offset) => {
+                write!(f, "Invalid line offset {} on line {}", offset, line_num)
+            }
         }
     }
 }
 
-pub type Scope<'a> = BTreeMap<&'a str, i32>;
+fn offset_line(line_num: usize, offset: i32) -> Result<usize, EvalError> {
+    if (line_num as i32) + offset < 0 {
+        Err(EvalError::OffsetError(line_num, offset))
+    } else {
+        Ok(((line_num as i32) + offset) as usize)
+    }
+}
 
 /// ## Evaluating expressions
 /// Now that we have a parsed file, that file has a bunch of numeric symbols in it: labels,
@@ -45,21 +55,22 @@ pub type Scope<'a> = BTreeMap<&'a str, i32>;
 /// - If the node is an absolute or relative line offset, it attempts to look up the start of
 ///   the given line in the table of line start addresses and gives that address relatively or
 ///   absolutely.
-pub fn eval<'a>(
-    node: &Node<'a>,
-    line_num: i32,
-    line_addresses: &BTreeMap<i32, i32>,
+pub fn eval(
+    node: &Node,
+    line_num: usize,
+    line_addresses: &BTreeMap<usize, i32>,
     scope: &Scope,
-) -> Result<i32, EvalError<'a>> {
+) -> Result<i32, EvalError> {
     match node {
         Node::Number(n) => Ok(*n),
-        Node::Label(label) => scope
-            .get(label)
-            .map_or_else(|| Err(EvalError::MissingLabel(label)), |val| Ok(*val)),
+        Node::Label(label) => scope.get(label.into()).map_or_else(
+            || Err(EvalError::MissingLabel(label.to_string())),
+            |val| Ok(*val),
+        ),
         Node::RelativeLabel(label) => {
             if let Some(address) = line_addresses.get(&line_num) {
-                scope.get(label).map_or_else(
-                    || Err(EvalError::MissingLabel(label)),
+                scope.get(label.into()).map_or_else(
+                    || Err(EvalError::MissingLabel(label.to_string())),
                     |val| Ok(*val - address),
                 )
             } else {
@@ -67,20 +78,21 @@ pub fn eval<'a>(
             }
         }
         Node::AbsoluteOffset(offset) => {
-            if let Some(dest_address) = line_addresses.get(&(line_num + offset)) {
+            let addr = offset_line(line_num, *offset)?;
+            if let Some(dest_address) = line_addresses.get(&addr) {
                 Ok(*dest_address)
             } else {
-                Err(EvalError::UnknownAddress(line_num + offset))
+                Err(EvalError::UnknownAddress(addr))
             }
         }
         Node::RelativeOffset(offset) => {
-            if let (Some(line_address), Some(dest_address)) = (
-                line_addresses.get(&line_num),
-                line_addresses.get(&(line_num + offset)),
-            ) {
+            let addr = offset_line(line_num, *offset)?;
+            if let (Some(line_address), Some(dest_address)) =
+                (line_addresses.get(&line_num), line_addresses.get(&addr))
+            {
                 Ok(*dest_address - *line_address)
             } else {
-                Err(EvalError::UnknownAddress(line_num + offset))
+                Err(EvalError::UnknownAddress(addr))
             }
         }
         Node::Expr(car, cdr) => {
@@ -114,25 +126,22 @@ mod test {
         test_scope_addresses_eval(BTreeMap::new(), [(1, 0x400)].into(), line)
     }
 
-    fn test_scope_eval<'a>(
-        scope: BTreeMap<&'a str, i32>,
-        line: &'a str,
-    ) -> Result<i32, EvalError<'a>> {
+    fn test_scope_eval(scope: Scope, line: &str) -> Result<i32, EvalError> {
         test_scope_addresses_eval(scope, [(1, 0x400)].into(), line)
     }
 
     fn test_addresses_eval(
-        line_addresses: BTreeMap<i32, i32>,
+        line_addresses: BTreeMap<usize, i32>,
         line: &str,
     ) -> Result<i32, EvalError> {
         test_scope_addresses_eval([].into(), line_addresses, line)
     }
 
-    fn test_scope_addresses_eval<'a>(
-        scope: BTreeMap<&'a str, i32>,
-        line_addresses: BTreeMap<i32, i32>,
-        line: &'a str,
-    ) -> Result<i32, EvalError<'a>> {
+    fn test_scope_addresses_eval(
+        scope: Scope,
+        line_addresses: BTreeMap<usize, i32>,
+        line: &str,
+    ) -> Result<i32, EvalError> {
         if let Ok(VASMLine::Instruction(_, _, Some(arg))) = parse_vasm_line(line) {
             eval(&arg, 1, &line_addresses, &scope)
         } else {
@@ -152,45 +161,51 @@ mod test {
 
     #[test]
     fn test_labels() {
-        assert_eq!(test_scope_eval([("apple", 5)].into(), "add apple"), Ok(5));
         assert_eq!(
-            test_scope_eval([("apple", 5)].into(), "add apple + 7"),
+            test_scope_eval([("apple".into(), 5)].into(), "add apple"),
+            Ok(5)
+        );
+        assert_eq!(
+            test_scope_eval([("apple".into(), 5)].into(), "add apple + 7"),
             Ok(12)
         );
         assert_eq!(
-            test_scope_eval([("apple", 5)].into(), "add 5 + apple"),
+            test_scope_eval([("apple".into(), 5)].into(), "add 5 + apple"),
             Ok(10)
         );
         assert_eq!(
-            test_scope_eval([("apple", 5), ("banana", 3)].into(), "add apple * banana"),
+            test_scope_eval(
+                [("apple".into(), 5), ("banana".into(), 3)].into(),
+                "add apple * banana"
+            ),
             Ok(15)
         );
         assert_eq!(
-            test_scope_eval([("apple", 5)].into(), "add banana"),
-            Err(EvalError::MissingLabel("banana"))
+            test_scope_eval([("apple".into(), 5)].into(), "add banana"),
+            Err(EvalError::MissingLabel("banana".into()))
         );
         assert_eq!(
             test_scope_eval([].into(), "add apple + 2"),
-            Err(EvalError::MissingLabel("apple"))
+            Err(EvalError::MissingLabel("apple".into()))
         );
         assert_eq!(
             test_scope_eval([].into(), "add 2 + apple"),
-            Err(EvalError::MissingLabel("apple"))
+            Err(EvalError::MissingLabel("apple".into()))
         );
     }
 
     #[test]
     fn test_relative_labels() {
         assert_eq!(
-            test_scope_eval([("apple", 0x500)].into(), "jmpr @apple"),
+            test_scope_eval([("apple".into(), 0x500)].into(), "jmpr @apple"),
             Ok(0x100)
         );
         assert_eq!(
-            test_scope_eval([("apple", 0x300)].into(), "jmpr @apple"),
+            test_scope_eval([("apple".into(), 0x300)].into(), "jmpr @apple"),
             Ok(-256)
         );
         assert_eq!(
-            test_scope_addresses_eval([("apple", 0x300)].into(), [].into(), "jmpr @apple"),
+            test_scope_addresses_eval([("apple".into(), 0x300)].into(), [].into(), "jmpr @apple"),
             Err(EvalError::UnknownAddress(1))
         );
     }
diff --git a/vasm/src/vasm_parser.rs b/vasm/src/vasm_parser.rs
index ec16c0a..6ee1efe 100644
--- a/vasm/src/vasm_parser.rs
+++ b/vasm/src/vasm_parser.rs
@@ -4,7 +4,7 @@ use pest::Parser;
 
 use vcore::opcodes::Opcode;
 
-use crate::ast::{Label, Node, Operator, VASMLine};
+use crate::ast::{Label, Macro, Node, Operator, VASMLine};
 use crate::parse_error::ParseError;
 use std::str::FromStr;
 
@@ -134,18 +134,18 @@ fn parse(pair: Pair) -> Node {
         Rule::oct_number => {
             Node::Number(i32::from_str_radix(pair.as_str().get(2..).unwrap(), 8).unwrap())
         }
-        Rule::label => Node::Label(pair.as_str()),
-        Rule::relative_label => Node::RelativeLabel(pair.as_str().get(1..).unwrap()),
+        Rule::label => Node::label(pair.as_str()),
+        Rule::relative_label => Node::relative_label(pair.as_str().get(1..).unwrap()),
         Rule::absolute_line_offset | Rule::relative_line_offset => create_line_offset_node(pair),
         _ => unreachable!(),
     }
 }
 
 fn optional_label(pair: Option<Pair>) -> Option<Label> {
-    pair.map(|label| Label(label.only().as_str()))
+    pair.map(|label| Label::from(label.only().as_str()))
 }
 
-pub fn parse_vasm_line(line: &str) -> Result<VASMLine, ParseError<'_>> {
+pub fn parse_vasm_line(line: &str) -> Result<VASMLine, ParseError> {
     let line = VASMParser::parse(Rule::line, line)
         .map_err(|_| ParseError::LineParseFailure)?
         .next()
@@ -164,35 +164,51 @@ pub fn parse_vasm_line(line: &str) -> Result<VASMLine, ParseError<'_>> {
             let argument = iter
                 .next_if(|pair| pair.as_rule() == Rule::expr)
                 .map(|expr| shake(parse(expr)));
-            return Ok(VASMLine::Instruction(label, opcode, argument));
+            Ok(VASMLine::Instruction(label, opcode, argument))
         }
         Rule::db_word => {
             let mut iter = line.into_inner().peekable();
             let label = optional_label(iter.next_if(|pair| pair.as_rule() == Rule::label_def));
             let argument = shake(parse(iter.next().unwrap()));
-            return Ok(VASMLine::Db(label, argument));
+            Ok(VASMLine::Db(label, argument))
         }
         Rule::db_string => {
             let mut iter = line.into_inner().peekable();
             let label = optional_label(iter.next_if(|pair| pair.as_rule() == Rule::label_def));
             let argument = create_string(iter.next().unwrap());
-            return Ok(VASMLine::StringDb(label, argument));
+            Ok(VASMLine::StringDb(label, argument))
         }
         Rule::org_directive => {
             let mut iter = line.into_inner().peekable();
             let label = optional_label(iter.next_if(|pair| pair.as_rule() == Rule::label_def));
             let argument = shake(parse(iter.next().unwrap()));
-            return Ok(VASMLine::Org(label, argument));
+            Ok(VASMLine::Org(label, argument))
         }
         Rule::equ_directive => {
             let mut iter = line.into_inner();
-            let label = Label(iter.next().unwrap().only().as_str());
+            let label = Label::from(iter.next().unwrap().only().as_str());
             let argument = shake(parse(iter.next().unwrap()));
-            return Ok(VASMLine::Equ(label, argument));
-        }
-        Rule::label_def => {
-            return Ok(VASMLine::LabelDef(Label(line.only().as_str())));
+            Ok(VASMLine::Equ(label, argument))
         }
+        Rule::label_def => Ok(VASMLine::LabelDef(Label::from(line.only().as_str()))),
+        Rule::preprocessor => Ok(VASMLine::Macro(parse_macro(line))),
+        _ => unreachable!(),
+    }
+}
+
+fn parse_macro(line: Pair) -> Macro {
+    let pre = line.only();
+    match pre.as_rule() {
+        Rule::control => match pre.as_str() {
+            "if" => Macro::If,
+            "else" => Macro::Else,
+            "while" => Macro::While,
+            "until" => Macro::Until,
+            "do" => Macro::Do,
+            "end" => Macro::End,
+            _ => unreachable!(),
+        },
+        Rule::include => Macro::Include(create_string(pre.only())),
         _ => unreachable!(),
     }
 }
@@ -204,7 +220,7 @@ mod test {
     use super::*;
     use crate::ast::Operator;
 
-    fn number(number: i32) -> Node<'static> {
+    fn number(number: i32) -> Node {
         Node::Number(number)
     }
 
@@ -220,7 +236,7 @@ mod test {
         );
         assert_eq!(
             parse_vasm_line("blah"),
-            Err(ParseError::InvalidInstruction("blah"))
+            Err(ParseError::InvalidInstruction("blah".into()))
         );
         assert_eq!(parse_vasm_line("47"), Err(ParseError::LineParseFailure));
     }
@@ -234,7 +250,7 @@ mod test {
         assert_eq!(
             parse_vasm_line("blah: add 45"),
             Ok(VASMLine::Instruction(
-                Some(Label("blah")),
+                Some(Label::from("blah")),
                 Add,
                 Some(number(45))
             ))
@@ -273,7 +289,7 @@ mod test {
         );
         assert_eq!(
             parse_vasm_line("foo: .db 47"),
-            Ok(VASMLine::Db(Some(Label("foo")), number(47)))
+            Ok(VASMLine::Db(Some(Label::from("foo")), number(47)))
         );
     }
 
@@ -316,7 +332,7 @@ mod test {
                 Add,
                 Some(Node::Expr(
                     Box::from(Node::Number(2)),
-                    vec![(Operator::Add, Node::Label("foo"))]
+                    vec![(Operator::Add, Node::label("foo"))]
                 ))
             ))
         );
@@ -326,7 +342,7 @@ mod test {
                 None,
                 Add,
                 Some(Node::Expr(
-                    Box::from(Node::Label("foo")),
+                    Box::from(Node::label("foo")),
                     vec![(Operator::Add, Node::Number(2))]
                 ))
             ))
@@ -337,14 +353,14 @@ mod test {
     fn test_expr_labels() {
         assert_eq!(
             parse_vasm_line("loadw foo"),
-            Ok(VASMLine::Instruction(None, Loadw, Some(Node::Label("foo"))))
+            Ok(VASMLine::Instruction(None, Loadw, Some(Node::label("foo"))))
         );
         assert_eq!(
             parse_vasm_line("brz @blah"),
             Ok(VASMLine::Instruction(
                 None,
                 Brz,
-                Some(Node::RelativeLabel("blah"))
+                Some(Node::relative_label("blah"))
             ))
         )
     }
@@ -373,16 +389,16 @@ mod test {
     fn test_parse_labels() {
         assert_eq!(
             parse_vasm_line("foo: add"),
-            Ok(VASMLine::Instruction(Some(Label("foo")), Add, None))
+            Ok(VASMLine::Instruction(Some(Label::from("foo")), Add, None))
         );
         assert_eq!(
             parse_vasm_line("bar:"),
-            Ok(VASMLine::LabelDef(Label("bar")))
+            Ok(VASMLine::LabelDef(Label::from("bar")))
         );
         assert_eq!(
             parse_vasm_line("foo: add 43"),
             Ok(VASMLine::Instruction(
-                Some(Label("foo")),
+                Some(Label::from("foo")),
                 Add,
                 Some(number(43))
             ))
@@ -393,11 +409,20 @@ mod test {
     fn test_parse_directives() {
         assert_eq!(
             parse_vasm_line("foo: .equ 47"),
-            Ok(VASMLine::Equ(Label("foo"), number(47)))
+            Ok(VASMLine::Equ(Label::from("foo"), number(47)))
         );
         assert_eq!(
             parse_vasm_line(".org 0x400"),
             Ok(VASMLine::Org(None, number(1024)))
         );
     }
+
+    #[test]
+    fn test_parse_macros() {
+        assert_eq!(parse_vasm_line("#if"), Ok(VASMLine::Macro(Macro::If)));
+        assert_eq!(
+            parse_vasm_line("#include \"blah\""),
+            Ok(VASMLine::Macro(Macro::Include("blah".to_string())))
+        )
+    }
 }