Add "sym" and "def" instructions, add argument naming

Cargo.lock

@@ -176,6 +176,7 @@ dependencies = [
  "dyn-clonable",
  "log",
  "num-traits",
+ "parking_lot",
  "sexp",
  "thiserror",
 ]

crsn/Cargo.toml

@@ -12,3 +12,4 @@ anyhow = "1.0.32"
 dyn-clonable = "0.9.0"
 log = "0.4.11"
 num-traits = "0.2.12"
+parking_lot = "0.11.0"

crsn/src/asm/data/literal.rs

@@ -124,3 +124,6 @@ impl From<String> for RoutineName {
         Self(n)
     }
 }
+
+pub type RegisterAlias = String;
+pub type ConstantName = String;

crsn/src/asm/data/reg.rs

@@ -3,7 +3,7 @@ use std::fmt::{self, Display, Formatter};
 use crate::asm::error::CrsnError;
 
 /// Register name
-#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
 pub enum Register {
     /// Argument register, read-only
     Arg(u8),
@@ -24,13 +24,23 @@ impl Display for Register {
 }
 
 pub fn parse_reg(name: &str) -> anyhow::Result<Register> {
+    // TODO deduplicate code
     if let Some(rn) = name.strip_prefix("arg") {
+        if rn.chars().find(|c : &char| !c.is_ascii_digit()).is_some() {
+            Err(CrsnError::Parse(format!("Bad register: {}", name).into()))?;
+        }
         let val: u8 = rn.parse()?;
         Ok(Register::Arg(val))
     } else if let Some(rn) = name.strip_prefix("res") {
+        if rn.chars().find(|c : &char| !c.is_ascii_digit()).is_some() {
+            Err(CrsnError::Parse(format!("Bad register: {}", name).into()))?;
+        }
         let val: u8 = rn.parse()?;
         Ok(Register::Res(val))
     } else if let Some(rn) = name.strip_prefix("r") {
+        if rn.chars().find(|c : &char| !c.is_ascii_digit()).is_some() {
+            Err(CrsnError::Parse(format!("Bad register: {}", name).into()))?;
+        }
         let val: u8 = rn.parse()?;
         Ok(Register::Gen(val))
     } else {

crsn/src/asm/instr/flatten.rs

@@ -12,6 +12,12 @@ pub trait Flatten {
     fn flatten(self: Box<Self>, label_num: &AtomicU32) -> Result<Vec<Op>, CrsnError>;
 }
 
+impl Flatten for () {
+    fn flatten(self: Box<Self>, _label_num: &AtomicU32) -> Result<Vec<Op>, CrsnError> {
+        Ok(vec![])
+    }
+}
+
 impl Flatten for Instr {
     fn flatten(self: Box<Self>, label_num: &AtomicU32) -> Result<Vec<Op>, CrsnError> {
         let mut ops = vec![self.op];
@@ -58,12 +64,13 @@ impl Flatten for Vec<Box<dyn Flatten>> {
 impl Flatten for Routine {
     fn flatten(self: Box<Self>, label_num: &AtomicU32) -> Result<Vec<Op>, CrsnError> {
         let mut ops = vec![
+            BuiltinOp::Barrier(Some(format!("Routine \"{}\" start", self.name).into())).into(),
             BuiltinOp::Routine(self.name.clone()).into(),
         ];
 
         ops.extend(self.body.flatten(label_num)?);
 
-        ops.push(BuiltinOp::Barrier(Some(format!("Routine \"{}\" overrun", self.name).into())).into());
+        ops.push(BuiltinOp::Barrier(Some(format!("Routine \"{}\" end", self.name).into())).into());
 
         numbered_labels_to_skips(ops)
     }

crsn/src/asm/mod.rs

@@ -1,5 +1,7 @@
+use std::cell::RefCell;
 use std::sync::Arc;
 
+use crate::asm::parse::{ParserContext, ParserState};
 use crate::module::CrsnExtension;
 use crate::runtime::program::Program;
 
@@ -11,7 +13,16 @@ pub mod patches;
 
 /// Parse a program from string and assemble a low level instruction sequence from it.
 pub fn assemble(source: &str, parsers: Arc<Vec<Box<dyn CrsnExtension>>>) -> Result<Arc<Program>, error::CrsnError> {
-    let ops = parse::parse(source, &parsers)?;
+    let pcx = ParserContext {
+        parsers: &parsers,
+        state: RefCell::new(ParserState {
+            reg_aliases: Default::default(),
+            reg_alias_stack: vec![],
+            constants: Default::default(),
+        }),
+    };
+
+    let ops = parse::parse(source, &pcx)?;
 
     trace!("--- Compiled program ---");
     for (n, op) in ops.iter().enumerate() {

crsn/src/asm/parse/arg_parser.rs

@@ -2,31 +2,36 @@ use sexp::Sexp;
 
 use crate::asm::data::{Mask, Rd, RdData, RdObj, Wr};
 use crate::asm::parse::parse_data::{parse_rd, parse_wr};
+use crate::asm::parse::ParserContext;
 use crate::asm::parse::sexp_expect::expect_string_atom;
 
 /// Utility for argument parsing
-pub struct TokenParser {
+pub struct TokenParser<'a> {
     orig_len: usize,
     args: Vec<Sexp>,
+    pub pcx: &'a ParserContext<'a>,
 }
 
-impl IntoIterator for TokenParser {
+impl<'a> IntoIterator for TokenParser<'a> {
     type Item = Sexp;
     type IntoIter = std::vec::IntoIter<Sexp>;
 
     fn into_iter(mut self) -> Self::IntoIter {
+        // The vec is reversed so we can call "pop", but here we will iterate it as slice so it
+        // must be reversed to its original direction.
         self.args.reverse();
         self.args.into_iter()
     }
 }
 
-impl TokenParser {
+impl<'a> TokenParser<'a> {
     /// Create a new argument parser
-    pub fn new(mut args: Vec<Sexp>) -> Self {
+    pub fn new(mut args: Vec<Sexp>, pcx: &'a ParserContext) -> Self {
         args.reverse();
         Self {
             orig_len: args.len(),
             args,
+            pcx,
         }
     }
 
@@ -61,17 +66,19 @@ impl TokenParser {
 
     /// Get the next string entry
     pub fn next_string(&mut self) -> anyhow::Result<String> {
-        Ok(expect_string_atom(self.next())?)
+        let next = self.next();
+        let esa = expect_string_atom(next)?;
+        Ok(esa)
     }
 
     /// Get the next entry as read location
     pub fn next_rd(&mut self) -> anyhow::Result<Rd> {
-        parse_rd(self.next())
+        parse_rd(self.next(), self.pcx)
     }
 
     /// Get the next entry as read location
     pub fn next_rdobj(&mut self) -> anyhow::Result<RdObj> {
-        match parse_rd(self.next())? {
+        match parse_rd(self.next(), self.pcx)? {
             Rd(RdData::ObjectPtr(reg), Mask::FULL) => {
                 return Ok(RdObj::new(reg));
             }
@@ -83,6 +90,6 @@ impl TokenParser {
 
     /// Get the next entry as write location
     pub fn next_wr(&mut self) -> anyhow::Result<Wr> {
-        parse_wr(self.next())
+        parse_wr(self.next(), self.pcx)
     }
 }

crsn/src/asm/parse/mod.rs

@@ -1,7 +1,11 @@
+use std::cell::RefCell;
+use std::collections::HashMap;
 use std::sync::atomic::AtomicU32;
 
 pub use parse_instr::parse_instructions;
 
+use crate::asm::data::literal::{ConstantName, RegisterAlias, Value};
+use crate::asm::data::Register;
 use crate::asm::error::CrsnError;
 use crate::asm::instr::Op;
 use crate::asm::parse::sexp_expect::expect_list;
@@ -13,8 +17,27 @@ pub mod parse_data;
 pub mod sexp_expect;
 pub mod parse_op;
 pub mod arg_parser;
+pub mod parse_routine;
 
-pub fn parse(source: &str, parsers: &[Box<dyn CrsnExtension>]) -> Result<Vec<Op>, CrsnError> {
+pub struct ParserContext<'a> {
+    /// Extension modules
+    pub parsers: &'a [Box<dyn CrsnExtension>],
+    /// Mutable state
+    pub state: RefCell<ParserState>,
+}
+
+pub struct ParserState {
+    /// Register aliases within the routine
+    pub reg_aliases: HashMap<RegisterAlias, Register>,
+
+    /// The old reg aliases map is pushed here when entering a routine definition
+    pub reg_alias_stack: Vec<HashMap<RegisterAlias, Register>>,
+
+    /// Global constants
+    pub constants: HashMap<ConstantName, Value>,
+}
+
+pub fn parse(source: &str, parsers: &ParserContext) -> Result<Vec<Op>, CrsnError> {
     let items = expect_list(Some(sexp::parse(source)?), true)?;
 
     let label_num = AtomicU32::new(0);

crsn/src/asm/parse/parse_cond.rs

@@ -3,11 +3,11 @@ use sexp::Sexp;
 use crate::asm::error::CrsnError;
 use crate::asm::instr::{Cond, cond, Flatten};
 use crate::asm::parse::parse_instr::parse_instructions;
+use crate::asm::parse::ParserContext;
 use crate::asm::parse::sexp_expect::{expect_list, expect_string_atom};
 use crate::asm::patches::TryRemove;
-use crate::module::CrsnExtension;
 
-pub fn parse_cond_branch(tok: Sexp, parsers: &[Box<dyn CrsnExtension>]) -> Result<(Cond, Box<dyn Flatten>), CrsnError> {
+pub fn parse_cond_branch(tok: Sexp, parsers: &ParserContext) -> Result<(Cond, Box<dyn Flatten>), CrsnError> {
     let mut list = expect_list(Some(tok), false)?;
     let kw = expect_string_atom(list.try_remove(0))?;
 

crsn/src/asm/parse/parse_data.rs

@@ -4,18 +4,54 @@ use std::convert::TryFrom;
 use sexp::{Atom, Sexp};
 
 use crate::asm::data::{DataDisp, Rd, RdData, reg, Wr, WrData};
-use crate::asm::data::literal::Label;
+use crate::asm::data::literal::{ConstantName, Label, RegisterAlias, Value};
 use crate::asm::error::CrsnError;
+use crate::asm::parse::ParserContext;
 use crate::asm::parse::sexp_expect::expect_string_atom;
 
+fn is_valid_identifier(name: &str) -> bool {
+    name.starts_with(|c: char| c.is_ascii_alphabetic() || c == '_')
+        && name.chars().find(|c| !c.is_ascii_alphanumeric() && *c != '_').is_none()
+}
+
+/// Parse register alias
+pub fn parse_reg_alias(name: Option<Sexp>) -> Result<RegisterAlias, CrsnError> {
+    trace!("parse reg alias: {:?}", name);
+
+    let name = expect_string_atom(name)?;
+
+    if !is_valid_identifier(&name) {
+        return Err(CrsnError::Parse(format!("\"{}\" is not an allowed register alias.", name).into()));
+    }
+
+    Ok(name)
+}
+
+/// Parse constant name
+pub fn parse_constant_name(name: Option<Sexp>) -> Result<ConstantName, CrsnError> {
+    trace!("parse const name: {:?}", name);
+
+    let name = expect_string_atom(name)?;
+
+    if !is_valid_identifier(&name) {
+        return Err(CrsnError::Parse(format!("\"{}\" is not an allowed constant name.", name).into()));
+    }
+
+    Ok(name)
+}
+
 /// Parse a label
 pub fn parse_label(name: Option<Sexp>) -> Result<Label, CrsnError> {
+    trace!("parse label: {:?}", name);
+
     let name = expect_string_atom(name)?;
     Ok(Label::Named(name.trim_start_matches(':').into()))
 }
 
 /// Parse data disposition (address/value, without the read/write restriction)
-pub fn parse_data_disp(tok: Option<Sexp>) -> Result<DataDisp, CrsnError> {
+pub fn parse_data_disp(tok: Option<Sexp>, pcx: &ParserContext) -> Result<DataDisp, CrsnError> {
+    trace!("parse data: {:?}", tok);
+
     let tok = if let Some(tok) = tok {
         tok
     } else {
@@ -33,6 +69,18 @@ pub fn parse_data_disp(tok: Option<Sexp>) -> Result<DataDisp, CrsnError> {
                 return Ok(DataDisp::Discard);
             }
 
+            // check if we have an alias defined
+            {
+                let pstate = pcx.state.borrow();
+                if let Some(val) = pstate.constants.get(s) {
+                    return Ok(DataDisp::Immediate(*val));
+                }
+
+                if let Some(val) = pstate.reg_aliases.get(s) {
+                    return Ok(DataDisp::Register(*val));
+                }
+            }
+
             if let Some(reference) = s.strip_prefix('@') {
                 Ok(DataDisp::ObjectPtr(reg::parse_reg(reference)?))
             } else if s.starts_with(|c: char| c.is_ascii_digit()) {
@@ -47,7 +95,32 @@ pub fn parse_data_disp(tok: Option<Sexp>) -> Result<DataDisp, CrsnError> {
     }
 }
 
+/// Parse immediate value
+pub fn parse_value(tok: Option<Sexp>) -> Result<Value, CrsnError> {
+    let tok = if let Some(tok) = tok {
+        tok
+    } else {
+        return Err(CrsnError::Parse("Expected value token".into()));
+    };
+
+    trace!("parse value: {:?}", tok);
+
+    match &tok {
+        Sexp::Atom(Atom::I(val)) => {
+            Ok(unsafe { std::mem::transmute(*val) })
+        }
+        Sexp::Atom(Atom::S(s)) => {
+            Ok(unsafe { std::mem::transmute(parse_i64(s)?) })
+        }
+        _ => {
+            Err(CrsnError::Parse(format!("bad value format: {:?}", tok).into()))
+        }
+    }
+}
+
+
 pub fn parse_u64(literal: &str) -> anyhow::Result<u64> {
+    trace!("parse u64 from {}", literal);
     let mut without_underscores = Cow::Borrowed(literal);
     if without_underscores.contains('_') {
         without_underscores = without_underscores.replace('_', "").into();
@@ -63,6 +136,7 @@ pub fn parse_u64(literal: &str) -> anyhow::Result<u64> {
 }
 
 pub fn parse_i64(literal: &str) -> anyhow::Result<i64> {
+    trace!("parse i64 from {}", literal);
     if let Some(_value) = literal.strip_prefix("-") {
         Ok(-1 * i64::try_from(parse_u64(literal)?)?)
     } else {
@@ -70,10 +144,10 @@ pub fn parse_i64(literal: &str) -> anyhow::Result<i64> {
     }
 }
 
-pub fn parse_rd(tok: Option<Sexp>) -> anyhow::Result<Rd> {
-    Ok(Rd::new(RdData::try_from(parse_data_disp(tok)?)?))
+pub fn parse_rd(tok: Option<Sexp>, pcx: &ParserContext) -> anyhow::Result<Rd> {
+    Ok(Rd::new(RdData::try_from(parse_data_disp(tok, pcx)?)?))
 }
 
-pub fn parse_wr(tok: Option<Sexp>) -> anyhow::Result<Wr> {
-    Ok(Wr::new(WrData::try_from(parse_data_disp(tok)?)?))
+pub fn parse_wr(tok: Option<Sexp>, pcx: &ParserContext) -> anyhow::Result<Wr> {
+    Ok(Wr::new(WrData::try_from(parse_data_disp(tok, pcx)?)?))
 }

crsn/src/asm/parse/parse_instr.rs

@@ -1,17 +1,21 @@
 use sexp::Sexp;
 
 use crate::asm::data::literal::RoutineName;
+use crate::asm::data::Register;
 use crate::asm::error::CrsnError;
 use crate::asm::instr::{Flatten, Instr, Routine};
 use crate::asm::parse::arg_parser::TokenParser;
 use crate::asm::parse::parse_cond::parse_cond_branch;
+use crate::asm::parse::parse_data::parse_reg_alias;
+use crate::asm::parse::ParserContext;
 use crate::asm::parse::sexp_expect::{expect_list, expect_string_atom};
 use crate::asm::patches::SexpIsA;
-use crate::module::{CrsnExtension, ParseRes};
+use crate::module::ParseRes;
 
 use super::parse_op::parse_op;
+use crate::asm::parse::parse_routine::parse_routine;
 
-pub fn parse_instructions(items: impl Iterator<Item=Sexp>, parsers: &[Box<dyn CrsnExtension>]) -> Result<Box<dyn Flatten>, CrsnError> {
+pub fn parse_instructions(items: impl Iterator<Item=Sexp>, pcx: &ParserContext) -> Result<Box<dyn Flatten>, CrsnError> {
     let mut parsed = vec![];
     for expr in items {
         let tokens = expect_list(Some(expr), false)?;
@@ -20,14 +24,15 @@ pub fn parse_instructions(items: impl Iterator<Item=Sexp>, parsers: &[Box<dyn Cr
         let name = expect_string_atom(toki.next())?;
 
         if name == "proc" {
-            parsed.push(parse_routine(toki, parsers)?);
+            parsed.push(parse_routine(toki, pcx)?);
             continue;
         }
 
-        let mut token_parser = TokenParser::new(toki.collect());
-        for p in parsers {
-            token_parser = match p.parse_syntax(&name, token_parser, parsers) {
+        let mut token_parser = TokenParser::new(toki.collect(), pcx);
+        for p in pcx.parsers {
+            token_parser = match p.parse_syntax(&name, token_parser) {
                 Ok(ParseRes::Parsed(op)) => return Ok(op),
+                Ok(ParseRes::ParsedNone) => return Ok(Box::new(())),
                 Ok(ParseRes::Unknown(to_reuse)) => {
                     if to_reuse.parsing_started() {
                         panic!("Module \"{}\" started parsing syntax, but returned Unknown!", p.name());
@@ -43,7 +48,7 @@ pub fn parse_instructions(items: impl Iterator<Item=Sexp>, parsers: &[Box<dyn Cr
         // Get back the original iterator
         let toki = token_parser.into_iter();
 
-        let arg_tokens = TokenParser::new(toki.clone().take_while(|e| e.is_atom()).collect());
+        let arg_tokens = TokenParser::new(toki.clone().take_while(|e| e.is_atom()).collect(), pcx);
         let branch_tokens = toki
             .skip_while(|e| e.is_atom())
             .take_while(|e| e.is_list());
@@ -51,7 +56,7 @@ pub fn parse_instructions(items: impl Iterator<Item=Sexp>, parsers: &[Box<dyn Cr
         let branches = {
             let mut branches = vec![];
             for t in branch_tokens {
-                branches.push(parse_cond_branch(t, parsers)?);
+                branches.push(parse_cond_branch(t, pcx)?);
             }
             if branches.is_empty() {
                 None
@@ -60,25 +65,12 @@ pub fn parse_instructions(items: impl Iterator<Item=Sexp>, parsers: &[Box<dyn Cr
             }
         };
 
+        if let Some(op) = parse_op(name.as_str(), arg_tokens)? {
             parsed.push(Box::new(Instr {
-            op: parse_op(name.as_str(), arg_tokens, parsers)?,
+                op,
                 branches,
             }));
         }
-    Ok(Box::new(parsed))
     }
-
-fn parse_routine(mut toki: impl Iterator<Item=Sexp> + Clone, parsers: &[Box<dyn CrsnExtension>]) -> Result<Box<dyn Flatten>, CrsnError> {
-    let name = expect_string_atom(toki.next())?;
-
-    let _arg_tokens = TokenParser::new(toki.clone().take_while(|e| e.is_atom()).collect());
-
-    // TODO parse arg tokens
-
-    let body = parse_instructions(toki, parsers)?;
-
-    return Ok(Box::new(Routine {
-        name: RoutineName(name),
-        body,
-    }));
+    Ok(Box::new(parsed))
 }

crsn/src/asm/parse/parse_op.rs

@@ -2,15 +2,16 @@ use crate::asm::error::CrsnError;
 use crate::asm::instr::Op;
 use crate::asm::parse::arg_parser::TokenParser;
 use crate::builtin::parse::BuiltinOps;
-use crate::module::{CrsnExtension, ParseRes};
+use crate::module::ParseRes;
 
-pub fn parse_op(keyword: &str, mut arg_tokens: TokenParser, parsers: &[Box<dyn CrsnExtension>]) -> Result<Op, CrsnError> {
+pub fn parse_op<'a>(keyword: &str, mut arg_tokens: TokenParser<'a>) -> Result<Option<Op>, CrsnError> {
     // Include built-in instructions
     let builtins = [BuiltinOps::new()];
 
-    for p in builtins.iter().chain(parsers) {
+    for p in builtins.iter().chain(arg_tokens.pcx.parsers) {
         arg_tokens = match p.parse_op(keyword, arg_tokens) {
-            Ok(ParseRes::Parsed(op)) => return Ok(op),
+            Ok(ParseRes::Parsed(op)) => return Ok(Some(op)),
+            Ok(ParseRes::ParsedNone) => return Ok(None),
             Ok(ParseRes::Unknown(to_reuse)) => {
                 if to_reuse.parsing_started() {
                     panic!("Module \"{}\" started parsing {}, but returned Unknown!", p.name(), keyword);

crsn/src/asm/parse/parse_routine.rs

@@ -0,0 +1,47 @@
+use sexp::Sexp;
+use crate::asm::parse::{ParserContext, parse_instructions};
+use crate::asm::instr::{Flatten, Routine};
+use crate::asm::error::CrsnError;
+use crate::asm::parse::sexp_expect::expect_string_atom;
+use crate::asm::parse::arg_parser::TokenParser;
+use crate::asm::patches::SexpIsA;
+use crate::asm::parse::parse_data::parse_reg_alias;
+use crate::asm::data::Register;
+use crate::asm::data::literal::RoutineName;
+
+pub fn parse_routine(mut toki: impl Iterator<Item=Sexp> + Clone, pcx: &ParserContext) -> Result<Box<dyn Flatten>, CrsnError> {
+    let name = expect_string_atom(toki.next())?;
+
+    let arg_tokens = TokenParser::new(toki.clone().take_while(|e| e.is_atom()).collect(), pcx);
+    let toki = toki.skip_while(|e| e.is_atom());
+
+    {
+        let mut pstate = pcx.state.borrow_mut();
+
+        let old = std::mem::replace(&mut pstate.reg_aliases, Default::default());
+        pstate.reg_alias_stack.push(old);
+
+        for (n, tok) in arg_tokens.into_iter().enumerate() {
+            let alias = parse_reg_alias(Some(tok))?;
+
+            if pstate.constants.contains_key(&alias) {
+                return Err(CrsnError::Parse(format!("Symbol \"{}\" already used for a constant.", alias).into()));
+            }
+
+            pstate.reg_aliases.insert(alias, Register::Arg(n as u8));
+        }
+    }
+
+    let body = parse_instructions(toki, pcx)?;
+
+    {
+        let mut pstate = pcx.state.borrow_mut();
+        let old = pstate.reg_alias_stack.pop().unwrap();
+        pstate.reg_aliases = old;
+    }
+
+    return Ok(Box::new(Routine {
+        name: RoutineName(name),
+        body,
+    }));
+}

crsn/src/builtin/parse.rs

@@ -1,11 +1,12 @@
 use sexp::{Atom, Sexp};
 
 use crate::asm::data::literal::{Label, RoutineName};
+use crate::asm::data::reg::parse_reg;
 use crate::asm::error::CrsnError;
 use crate::asm::instr::cond::parse_cond;
 use crate::asm::instr::Op;
 use crate::asm::parse::arg_parser::TokenParser;
-use crate::asm::parse::parse_data::{parse_label, parse_rd};
+use crate::asm::parse::parse_data::{parse_constant_name, parse_label, parse_rd, parse_reg_alias, parse_value};
 use crate::asm::parse::sexp_expect::expect_string_atom;
 use crate::builtin::defs::BuiltinOp;
 use crate::module::{CrsnExtension, ParseRes};
@@ -28,7 +29,9 @@ impl CrsnExtension for BuiltinOps {
         "builtin"
     }
 
-    fn parse_op(&self, keyword: &str, mut args: TokenParser) -> Result<ParseRes<Op>, CrsnError> {
+    fn parse_op<'a>(&self, keyword: &str, mut args: TokenParser<'a>) -> Result<ParseRes<'a, Op>, CrsnError> {
+        let pcx = args.pcx;
+
         Ok(ParseRes::Parsed(Op::BuiltIn(match keyword {
             "nop" => {
                 BuiltinOp::Nop
@@ -44,6 +47,48 @@ impl CrsnExtension for BuiltinOps {
                 }
             }
 
+            "sym" => {
+                let alias = parse_reg_alias(args.next())?;
+                trace!("alias={:?}", alias);
+                let register = parse_reg(&args.next_string()?)?;
+                trace!("register={:?}", alias);
+
+                let mut pstate = pcx.state.borrow_mut();
+                if pstate.reg_aliases.contains_key(&alias) {
+                    return Err(CrsnError::Parse(format!("Register alias \"{}\" already defined!", alias).into()));
+                }
+
+                if pstate.constants.contains_key(&alias) {
+                    return Err(CrsnError::Parse(format!("Name \"{}\" already used for a constant!", alias).into()));
+                }
+
+                if pstate.reg_aliases.iter().find(|x| x.1 == &register).is_some() {
+                    return Err(CrsnError::Parse(format!("Register \"{}\" already aliased!", register).into()));
+                }
+
+                pstate.reg_aliases.insert(alias, register);
+
+                return Ok(ParseRes::ParsedNone);
+            }
+
+            "def" => {
+                let name = parse_constant_name(args.next())?;
+                let value = parse_value(args.next())?;
+
+                let mut pstate = pcx.state.borrow_mut();
+                if pstate.constants.contains_key(&name) {
+                    return Err(CrsnError::Parse(format!("Constant \"{}\" already defined!", name).into()));
+                }
+
+                if pstate.reg_aliases.contains_key(&name) {
+                    return Err(CrsnError::Parse(format!("Name \"{}\" already used for a register alias!", name).into()));
+                }
+
+                pstate.constants.insert(name, value);
+
+                return Ok(ParseRes::ParsedNone);
+            }
+
             "j" => {
                 let dest = parse_label(args.next())?;
                 BuiltinOp::Jump(dest)
@@ -59,7 +104,7 @@ impl CrsnExtension for BuiltinOps {
 
                 let mut call_args = vec![];
                 for t in args {
-                    call_args.push(parse_rd(Some(t))?);
+                    call_args.push(parse_rd(Some(t), pcx)?);
                 }
                 BuiltinOp::Call(dest, call_args)
             }
@@ -67,7 +112,7 @@ impl CrsnExtension for BuiltinOps {
             "ret" => {
                 let mut ret_vals = vec![];
                 for t in args {
-                    ret_vals.push(parse_rd(Some(t))?);
+                    ret_vals.push(parse_rd(Some(t), pcx)?);
                 }
                 BuiltinOp::Ret(ret_vals)
             }
@@ -77,11 +122,13 @@ impl CrsnExtension for BuiltinOps {
                 BuiltinOp::Routine(dest)
             }
 
-            "s" => {
+            "sk" => {
                 BuiltinOp::Skip(args.next_rd()?)
             }
 
-            "sif" => {
+            // TODO add jne-style names for jif ne ...
+
+            "skif" => {
                 let cond = parse_cond(&args.next_string()?)?;
                 let offs = args.next_rd()?;
                 BuiltinOp::SkipIf(cond, offs)

crsn/src/module/mod.rs

@@ -16,14 +16,16 @@ use crate::runtime::run_thread::ThreadInfo;
 mod eval_res;
 
 /// Result type returned from the op parser. This is the Ok variant of a Result.
-pub enum ParseRes<T> {
+pub enum ParseRes<'a, T> {
     /// Parsing successful.
     Parsed(T),
+    /// Parsing successful, but did not yield any result
+    ParsedNone,
     /// Instruction not recognized, but there was no error.
-    Unknown(TokenParser),
+    Unknown(TokenParser<'a>),
 }
 
-impl ParseRes<Op> {
+impl<'a> ParseRes<'a, Op> {
     /// Helper to construct an extension op
     pub fn ext(op: impl OpTrait) -> Self {
         Self::Parsed(Op::Ext(Box::new(op)))
@@ -43,11 +45,15 @@ pub trait CrsnExtension: Debug + Send + Sync + 'static {
     /// the argument list and either return Ok or Err.
     ///
     /// If the instruction keyword is not recognized, return Unknown with the unchanged argument list.
-    fn parse_op(&self, keyword: &str, arg_tokens: TokenParser) -> Result<ParseRes<Op>, CrsnError>;
+    ///
+    /// pcx is available on the arg_tokens parser
+    fn parse_op<'a>(&self, keyword: &str, arg_tokens: TokenParser<'a>) -> Result<ParseRes<'a, Op>, CrsnError>;
 
     /// Parse a generic S-expression (non-op)
-    fn parse_syntax(&self, keyword: &str, tokens: TokenParser, parsers: &[Box<dyn CrsnExtension>])
-                    -> Result<ParseRes<Box<dyn Flatten>>, CrsnError>
+    ///
+    /// pcx is available on the arg_tokens parser
+    fn parse_syntax<'a>(&self, keyword: &str, tokens: TokenParser<'a>)
+                        -> Result<ParseRes<'a, Box<dyn Flatten>>, CrsnError>
     {
         Ok(ParseRes::Unknown(tokens))
     }

crsn_arith/src/lib.rs

@@ -21,7 +21,7 @@ impl CrsnExtension for ArithOps {
         "arith"
     }
 
-    fn parse_op(&self, keyword: &str, args: TokenParser) -> Result<ParseRes<Op>, CrsnError> {
+    fn parse_op<'a>(&self, keyword: &str, args: TokenParser<'a>) -> Result<ParseRes<'a, Op>, CrsnError> {
         parse::parse(keyword, args)
     }
 }

crsn_arith/src/parse.rs

@@ -6,7 +6,7 @@ use crsn::module::ParseRes;
 
 use crate::defs::ArithOp;
 
-pub(crate) fn parse(keyword: &str, mut args: TokenParser) -> Result<ParseRes<Op>, CrsnError> {
+pub(crate) fn parse<'a>(keyword: &str, mut args: TokenParser<'a>) -> Result<ParseRes<'a, Op>, CrsnError> {
     Ok(ParseRes::ext(match keyword {
         "cmp" => {
             ArithOp::Compare {

crsn_screen/src/lib.rs

@@ -24,7 +24,7 @@ impl CrsnExtension for ScreenOps {
         "screen"
     }
 
-    fn parse_op(&self, keyword: &str, args: TokenParser) -> Result<ParseRes<Op>, CrsnError> {
+    fn parse_op<'a>(&self, keyword: &str, args: TokenParser<'a>) -> Result<ParseRes<'a, Op>, CrsnError> {
         parse::parse(keyword, args)
     }
 }

crsn_screen/src/parse.rs

@@ -6,7 +6,7 @@ use crsn::module::ParseRes;
 
 use crate::defs::ScreenOp;
 
-pub(crate) fn parse(keyword: &str, mut args: TokenParser) -> Result<ParseRes<Op>, CrsnError> {
+pub(crate) fn parse<'a>(keyword: &str, mut args: TokenParser<'a>) -> Result<ParseRes<'a, Op>, CrsnError> {
     Ok(ParseRes::ext(match keyword {
         "sc-init" => {
             ScreenOp::ScreenInit {

crsn_stacks/src/lib.rs

@@ -24,7 +24,7 @@ impl CrsnExtension for StackOps {
         "stacks"
     }
 
-    fn parse_op(&self, keyword: &str, args: TokenParser) -> Result<ParseRes<Op>, CrsnError> {
+    fn parse_op<'a>(&self, keyword: &str, args: TokenParser<'a>) -> Result<ParseRes<'a, Op>, CrsnError> {
         parse::parse(keyword, args)
     }
 

crsn_stacks/src/parse.rs

@@ -5,7 +5,7 @@ use crsn::module::ParseRes;
 
 use crate::defs::StackOp;
 
-pub(crate) fn parse(keyword: &str, mut args: TokenParser) -> Result<ParseRes<Op>, CrsnError> {
+pub(crate) fn parse<'a>(keyword: &str, mut args: TokenParser<'a>) -> Result<ParseRes<'a, Op>, CrsnError> {
     Ok(ParseRes::ext(match keyword {
         "stack" => {
             StackOp::NewStack {

examples/aliases.csn

@@ -0,0 +1,13 @@
+(
+    (def FOO 123) ; define a constant
+    (call my-add 7 8)
+    (cmp res0 138 (ne? (fault "assert failed")))
+    (halt)
+
+    (proc my-add a b ; give arguments names
+        (sym q r0) ; give register a temporary alias
+        (add q a b)
+        (add q FOO)
+        (ret q)
+    )
+)

examples/factorial.csn

@@ -1,9 +1,8 @@
 (
-    (proc main
     (call fac 5)
     (ld r0 res0)
     (halt)
-    )
+
     (proc fac
         (cmp arg0 2
             (eq? (ret 2)))

examples/screen_bounce.csn

@@ -1,7 +1,5 @@
 ; Set log level to "info" or above for the best results!
-
 (
-    (proc main
     (sc-init 800 600)
     (sc-opt 1 1) ; auto blit
     (sc-opt 2 25) ; frame rate
@@ -22,5 +20,5 @@
         (cmp r0 799 (eq? (ld r2 -1)) (ne? (cmp r0 0 (eq? (ld r2 1)))))
         (cmp r1 599 (eq? (ld r3 -1)) (ne? (cmp r1 0 (eq? (ld r3 1)))))
     (j :loop)
-    )
+    (fault "unreachable")
 )