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-rw-r--r--src/forth/interp.rs273
1 files changed, 268 insertions, 5 deletions
diff --git a/src/forth/interp.rs b/src/forth/interp.rs
index 406c424..c7e8588 100644
--- a/src/forth/interp.rs
+++ b/src/forth/interp.rs
@@ -6,8 +6,14 @@ pub enum OpCode {
Num(i32),
Str(usize, usize),
Call(usize),
+ TCall(usize), // tail call, really just ‘jmp’, but named to indicate desired usage.
+ If(usize, Option<usize>), // true word index, optional false word index.
+ TIf(usize, Option<usize>), // tail version
Add,
Sub,
+ // todo: maybe get rid of ret? it's only used in word definitions,
+ // which are bounded, so running of the end can be treated as an
+ // implicit ‘ret’.
Ret,
}
@@ -28,7 +34,6 @@ impl Index<usize> for ByteCode {
}
}
-// .0 is wordlist entry's bytecode, .1 is index into that bytecode
#[derive(Debug, Copy, Clone, PartialEq)]
pub(super) struct InstructionPointer {
pub(super) word: usize,
@@ -79,8 +84,19 @@ impl Interp {
}
}
+ pub fn jmp(&mut self, word: usize) {
+ self.ip.word = word;
+ self.ip.offset = 0;
+ }
+
+ pub fn call(&mut self, word: usize) {
+ self.callstack.0.push(self.ip);
+ self.jmp(word);
+ }
+
pub fn tick(&mut self) -> Result<(), RuntimeError> {
let bc = &self.wordlist.0[self.ip.word];
+ eprintln!("debug: executing {:?}", bc[self.ip.offset]);
match bc[self.ip.offset] {
OpCode::Num(n) => self.stack.0.push(n),
OpCode::Str(start, end) => eprintln!("got str: {} to {}", start, end),
@@ -98,13 +114,45 @@ impl Interp {
self.ip = self.callstack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
},
OpCode::Call(i) => {
+ eprintln!("should call word based on index {}", i);
+ self.call(i);
+ // skip the offset increment
+ return Ok(())
+ },
+ OpCode::TCall(i) => {
eprintln!("should jump to word based on index {}", i);
- self.callstack.0.push(self.ip);
- self.ip.word = i;
- self.ip.offset = 0;
+ self.jmp(i);
// skip the offset increment
return Ok(())
- }
+ },
+ OpCode::If(true_clause, false_clause) => {
+ let flag = self.stack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
+ if flag != 0 {
+ eprintln!("should call true branch {}", true_clause);
+ self.call(true_clause);
+ return Ok(())
+ } else if let Some(false_clause) = false_clause {
+ eprintln!("should call false branch {}", false_clause);
+ self.call(false_clause);
+ return Ok(())
+ } else {
+ eprintln!("should false fall through");
+ }
+ },
+ OpCode::TIf(true_clause, false_clause) => {
+ let flag = self.stack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
+ if flag != 0 {
+ eprintln!("should call true branch {}", true_clause);
+ self.jmp(true_clause);
+ return Ok(())
+ } else if let Some(false_clause) = false_clause {
+ eprintln!("should call false branch {}", false_clause);
+ self.jmp(false_clause);
+ return Ok(())
+ } else {
+ eprintln!("should false fall through");
+ }
+ },
}
self.ip.offset += 1;
Ok(())
@@ -193,4 +241,219 @@ mod tests {
Ok(())
}
+
+ #[test]
+ fn tail_call() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Call(1)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::TCall(2), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Ret]));
+
+
+ interp.tick()?; // call
+ assert_eq!(interp.callstack.0.len(), 1, "callstack after call");
+ interp.tick()?; // tcall
+ assert_eq!(interp.callstack.0.len(), 1, "callstack after tcall");
+ interp.tick()?; // ret
+ assert_eq!(interp.callstack.0.len(), 0, "callstack after ret");
+ Ok(())
+ }
+
+ #[test]
+ fn if_then_true() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(-1), OpCode::If(1, None), OpCode::Num(0)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push -1 stack len");
+ assert_eq!(interp.stack.0[0], -1, "push -1 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "if stack ");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 1 stack len");
+ assert_eq!(interp.stack.0[0], 1, "push 1 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "ret stack len");
+ assert_eq!(interp.stack.0[0], 1, "ret stack val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 2, "push 0 stack len");
+ assert_eq!(interp.stack.0[1], 0, "push 0 stack val");
+
+ Ok(())
+ }
+
+ #[test]
+ fn if_then_false() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(0), OpCode::If(1, None), OpCode::Num(-1)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 0 stack len");
+ assert_eq!(interp.stack.0[0], 0, "push 0 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "if stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push -1 stack len");
+ assert_eq!(interp.stack.0[0], -1, "push -1 val");
+
+ Ok(())
+ }
+
+ #[test]
+ fn if_else_then_true() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(-1), OpCode::If(1, Some(2)), OpCode::Num(-2)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(2), OpCode::Ret]));
+
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push -1 stack len");
+ assert_eq!(interp.stack.0[0], -1, "push -1 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "if stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 1 stack len");
+ assert_eq!(interp.stack.0[0], 1, "push 1 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "ret stack len");
+ assert_eq!(interp.stack.0[0], 1, "ret val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 2, "push -2 stack len");
+ assert_eq!(interp.stack.0[1], -2, "push -2 val");
+
+ Ok(())
+ }
+
+ #[test]
+ fn if_else_then_false() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(0), OpCode::If(1, Some(2)), OpCode::Num(-2)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(2), OpCode::Ret]));
+
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 0 stack len");
+ assert_eq!(interp.stack.0[0], 0, "push 0 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "if");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 2 stack len");
+ assert_eq!(interp.stack.0[0], 2, "push 2 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "ret");
+ assert_eq!(interp.stack.0[0], 2, "ret");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 2, "push -2 stack len");
+ assert_eq!(interp.stack.0[1], -2, "push -2 val");
+
+ Ok(())
+ }
+
+ #[test]
+ fn tail_if_then_true() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Call(1), OpCode::Num(0)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(-1), OpCode::TIf(2, None), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "call(1) stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push -1 stack len");
+ assert_eq!(interp.stack.0[0], -1, "push -1 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "tif stack ");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 1 stack len");
+ assert_eq!(interp.stack.0[0], 1, "push 1 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "ret stack len");
+ assert_eq!(interp.stack.0[0], 1, "ret stack val");
+ interp.tick()?; // no ret on wordlist[1] since it's ‘tif’
+ assert_eq!(interp.stack.0.len(), 2, "push 0 stack len");
+ assert_eq!(interp.stack.0[1], 0, "push 0 stack val");
+
+ Ok(())
+ }
+
+ #[test]
+ fn tail_if_then_false() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Call(1), OpCode::Num(0)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(0), OpCode::TIf(2, None), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "call(1) stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 0 stack len");
+ assert_eq!(interp.stack.0[0], 0, "push 0 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "tif stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "ret stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 0 stack len");
+ assert_eq!(interp.stack.0[0], 0, "push 0 val");
+
+ Ok(())
+ }
+
+ #[test]
+ fn tail_if_else_then_true() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Call(1), OpCode::Num(-2)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(-1), OpCode::TIf(2, Some(3)), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(2), OpCode::Ret]));
+
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "call(1) stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push -1 stack len");
+ assert_eq!(interp.stack.0[0], -1, "push -1 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "tif stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 1 stack len");
+ assert_eq!(interp.stack.0[0], 1, "push 1 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "ret stack len");
+ assert_eq!(interp.stack.0[0], 1, "ret val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 2, "push -2 stack len");
+ assert_eq!(interp.stack.0[1], -2, "push -2 val");
+
+ Ok(())
+ }
+
+ #[test]
+ fn tail_if_else_then_false() -> Result<(), RuntimeError> {
+ let mut interp = Interp::new();
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Call(1), OpCode::Num(-2)]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(0), OpCode::TIf(2, Some(3)), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+ interp.wordlist.0.push(ByteCode(vec![OpCode::Num(2), OpCode::Ret]));
+
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "call(1) stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 0 stack len");
+ assert_eq!(interp.stack.0[0], 0, "push 0 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 0, "tif stack len");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "push 2 stack len");
+ assert_eq!(interp.stack.0[0], 2, "push 2 val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 1, "ret stack len");
+ assert_eq!(interp.stack.0[0], 2, "ret val");
+ interp.tick()?;
+ assert_eq!(interp.stack.0.len(), 2, "push -2 stack len");
+ assert_eq!(interp.stack.0[1], -2, "push -2 val");
+
+ Ok(())
+ }
}
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