rishi/scryer-prolog
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add preliminary support for DCGs.

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This commit is contained in:
Mark Thom
2018-10-07 00:07:12 -06:00
parent e7717d4f61
commit 59ad71fccc
7 changed files with 170 additions and 129 deletions
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51
src/prolog/heap_print.rs
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@@ -115,6 +115,29 @@ fn is_numbered_var(ct: &ClauseType, arity: usize) -> bool {
}
}
impl MachineState {
pub fn numbervar(&self, addr: Addr) -> Option<Var> {
static CHAR_CODES: [char; 26] = ['A','B','C','D','E','F','G','H','I','J',
'K','L','M','N','O','P','Q','R','S','T',
'U','V','W','X','Y','Z'];
match self.store(self.deref(addr)) {
Addr::Con(Constant::Number(Number::Integer(ref n)))
if !n.is_negative() => {
let i = n.mod_floor(&BigInt::from(26)).to_usize().unwrap();
let j = n.div_floor(&BigInt::from(26));
Some(if j.is_zero() {
CHAR_CODES[i].to_string()
} else {
format!("{}{}", CHAR_CODES[i], j)
})
},
_ => None
}
}
}
fn print_op(ct: ClauseType, fixity: Fixity, state_stack: &mut Vec<TokenOrRedirect>) {
match fixity {
Fixity::Post => {
@@ -137,35 +160,17 @@ impl HCValueFormatter for WriteqFormatter {
fn format_clause(&self, iter: &mut HCPreOrderIterator, arity: usize,
ct: ClauseType, state_stack: &mut Vec<TokenOrRedirect>)
{
static CHAR_CODES: [char; 26] = ['A','B','C','D','E','F','G','H','I','J',
'K','L','M','N','O','P','Q','R','S','T',
'U','V','W','X','Y','Z'];
if let Some(fixity) = ct.fixity() {
return print_op(ct, fixity, state_stack);
} else if is_numbered_var(&ct, arity) {
let addr = iter.stack().last().cloned().unwrap();
// 7.10.4
match iter.machine_st.store(iter.machine_st.deref(addr)) {
Addr::Con(Constant::Number(Number::Integer(ref n))) if !n.is_negative() => {
iter.stack().pop();
let i = n.mod_floor(&BigInt::from(26)).to_usize().unwrap();
let j = n.div_floor(&BigInt::from(26));
let mut result = if j.is_zero() {
CHAR_CODES[i].to_string()
} else {
format!("{}{}", CHAR_CODES[i], j)
};
state_stack.push(TokenOrRedirect::NumberedVar(result));
return;
}
_ => {}
};
if let Some(var) = iter.machine_st.numbervar(addr) {
iter.stack().pop();
state_stack.push(TokenOrRedirect::NumberedVar(var));
return;
}
}
self.format_struct(arity, ct.name(), state_stack);