Minor "else" improvements

- Do not generate s.never to skip Else branch
- Add Display impl to SourcePosition
- Correct SourcePositions pointing to the end of a parsed expr instead of the beginning
- Remove 'true', 'always', 'false' and 'never' from README.md
master
Ondřej Hruška 4 years ago
parent 0006cd06ec
commit 8d10fa406d
Signed by untrusted user: MightyPork
GPG Key ID: 2C5FD5035250423D
  1. 3
      README.md
  2. 6
      crsn/crsn-sexp/src/error.rs
  3. 5
      crsn/crsn-sexp/src/lib.rs
  4. 14
      crsn/src/asm/instr/flatten.rs
  5. 12
      crsn/src/asm/instr/op.rs
  6. 19
      examples/test_cond.csn

@ -98,8 +98,7 @@ These keywords (among others) are used in conditional branches to specify flag t
- `nem`, `nempty` … Not empty
- `eof` … EOF
- `neof` … Not EOF
- `true`, `always`, `else` … Always true
- `false`, `never` … Always false
- `else` … Always true, may be used in the last branch
# Syntax

@ -19,6 +19,12 @@ pub struct SourcePosition {
pub index: u32,
}
impl fmt::Display for SourcePosition {
fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
write!(f, "{}:{}", self.line, self.column)
}
}
/// Since errors are the uncommon case, they're boxed. This keeps the size of
/// structs down, which helps performance in the common case.
///

@ -331,10 +331,11 @@ fn parse_sexp(s: &str, pos: &mut usize) -> ERes<Sexp> {
//trace!("parse_sexp {}", pos);
zspace(s, pos)?;
let (c, _) = peek(s, *pos)?;
let pos0 = *pos;
let r = if c == '(' {
Ok(Sexp::List(parse_list(s, pos)?, spos(s, *pos)))
Ok(Sexp::List(parse_list(s, pos)?, spos(s, pos0)))
} else {
Ok(Sexp::Atom(parse_atom(s, pos)?, spos(s, *pos)))
Ok(Sexp::Atom(parse_atom(s, pos)?, spos(s, pos0)))
};
zspace(s, pos)?;
r

@ -50,7 +50,7 @@ impl Flatten for InstrWithBranches {
}
if cnt != branch_count - 1 && cond == Cond::True {
warn!("\"Else\" conditional used in non-final branch at {}:{}", branch.pos().line, branch.pos().column);
warn!("\"Else\" conditional used in non-final branch at {}", branch.pos());
}
let next_lbl = if cnt == branch_count - 1 {
@ -68,11 +68,13 @@ impl Flatten for InstrWithBranches {
// optimization for single-branch conditionals with a single instruction
ops.push(Op { cond: Some(cond), pos: pos.clone(), kind: flattened.remove(0).kind });
} else {
ops.push(Op {
kind: OpKind::BuiltIn(BuiltinOp::Jump(next_lbl.clone())),
pos: pos.clone(),
cond: Some(!cond),
});
if cond != Cond::True { // evoid emiting `op.never`
ops.push(Op {
kind: OpKind::BuiltIn(BuiltinOp::Jump(next_lbl.clone())),
pos: pos.clone(),
cond: Some(!cond),
});
}
ops.extend(flattened);
}

@ -50,11 +50,15 @@ impl OpTrait for Op {
OpKind::Ext(op) => op.to_sexp()
};
// TODO rewrite to be more readable?
if let Some(cond) = self.cond {
if let Sexp::List(items, _) = &mut se {
if let Some(Sexp::Atom(Atom::S(s), _)) = &mut items.get_mut(0) {
s.push('.');
s.push_str(&cond.to_string());
// "true" is used for "else" branches, it has no effect - just omit it
if cond != Cond::True {
if let Sexp::List(items, _) = &mut se {
if let Some(Sexp::Atom(Atom::S(s), _)) = &mut items.get_mut(0) {
s.push('.');
s.push_str(&cond.to_string());
}
}
}
}

@ -1,4 +1,23 @@
(
; test else
(cmp 0 5
(eq? (fault))
(else? (ld r0 15))
(lt? (fault)) ; This should produce a warning
)
(cmp 15 r0
(ne? (fault "else did not run")))
(ld r0 0)
(cmp 0 5
(lt? (nop))
(else? (fault "fallthrough to else"))
)
;
(ld r8 0)
(ld r0 1

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