remove vestigial prolog/ directory (#444)

src/indexing.rs

@@ -0,0 +1,369 @@
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
+
+use crate::instructions::*;
+use crate::rug::Integer;
+
+use crate::indexmap::IndexMap;
+
+use std::collections::VecDeque;
+use std::convert::TryFrom;
+use std::hash::Hash;
+use std::rc::Rc;
+
+#[derive(Debug, Clone, Copy)]
+enum IntIndex {
+    External(usize),
+    Fail,
+    Internal(usize),
+}
+
+#[derive(Debug)]
+pub struct CodeOffsets {
+    atom_tbl: TabledData<Atom>,
+    pub constants: IndexMap<Constant, ThirdLevelIndex>,
+    pub lists: ThirdLevelIndex,
+    pub structures: IndexMap<(ClauseName, usize), ThirdLevelIndex>,
+}
+
+impl CodeOffsets {
+    pub fn new() -> Self {
+        CodeOffsets {
+            atom_tbl: TabledData::new(Rc::new("_index".to_string())),
+            constants: IndexMap::new(),
+            lists: Vec::new(),
+            structures: IndexMap::new(),
+        }
+    }
+
+    fn cap_choice_seq_with_trust(prelude: &mut ThirdLevelIndex) {
+        prelude.last_mut().map(|instr| {
+            match instr {
+                &mut IndexedChoiceInstruction::Retry(i) => {
+                    *instr = IndexedChoiceInstruction::Trust(i)
+                }
+                _ => {}
+            };
+        });
+    }
+
+    fn add_index(is_first_index: bool, index: usize) -> IndexedChoiceInstruction {
+        if is_first_index {
+            IndexedChoiceInstruction::Try(index)
+        } else {
+            IndexedChoiceInstruction::Retry(index)
+        }
+    }
+
+    fn intercept_overlapping_constant(&mut self, constant: &Constant, index: usize) {
+        match constant {
+            &Constant::Atom(ref name, ref op) if name.is_char() => {
+                let c = name.as_str().chars().next().unwrap();
+                let code = self.constants
+                    .entry(Constant::Char(c))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+
+                if op.is_some() {
+                    let code = self.constants
+                        .entry(Constant::Atom(name.clone(), None))
+                        .or_insert(vec![]);
+
+                    code.push(Self::add_index(false, index));
+                }
+            }
+            &Constant::Atom(ref name, Some(_)) => {
+                let code = self.constants
+                    .entry(Constant::Atom(name.clone(), None))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+            }
+            &Constant::Char(c) => {
+                let atom = clause_name!(c.to_string(), self.atom_tbl.clone());
+
+                let code = self.constants
+                    .entry(Constant::Atom(atom, None))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+            }
+            &Constant::Fixnum(n) => {
+                let code = self.constants
+                    .entry(Constant::Integer(Rc::new(Integer::from(n))))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+
+                if n >= 0 {
+                    if let Ok(n) = usize::try_from(n) {
+                        let code = self.constants
+                            .entry(Constant::Usize(n))
+                            .or_insert(vec![]);
+
+                        code.push(Self::add_index(code.is_empty(), index));
+                    }
+                }
+            }
+            &Constant::Integer(ref n) => {
+                if let Some(n) = n.to_isize() {
+                    let code = self.constants
+                        .entry(Constant::Fixnum(n))
+                        .or_insert(vec![]);
+
+                    code.push(Self::add_index(code.is_empty(), index));
+                }
+
+                if let Some(n) = n.to_usize() {
+                    let code = self.constants
+                        .entry(Constant::Usize(n))
+                        .or_insert(vec![]);
+
+                    code.push(Self::add_index(code.is_empty(), index));
+                }
+            }
+            &Constant::String(_) => {
+                let is_initial_index = self.lists.is_empty();
+                self.lists.push(Self::add_index(is_initial_index, index));
+            }
+            &Constant::Usize(n) => {
+                let code = self.constants
+                    .entry(Constant::Integer(Rc::new(Integer::from(n))))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+
+                if let Ok(n) = isize::try_from(n) {
+                    let code = self.constants
+                        .entry(Constant::Fixnum(n))
+                        .or_insert(vec![]);
+
+                    code.push(Self::add_index(code.is_empty(), index));
+                }
+            }
+            _ => {
+            }
+        }
+    }
+
+    pub fn index_term(&mut self, first_arg: &Term, index: usize) {
+        match first_arg {
+            &Term::Clause(_, ref name, ref terms, _) => {
+                let code = self
+                    .structures
+                    .entry((name.clone(), terms.len()))
+                    .or_insert(Vec::new());
+
+                let is_initial_index = code.is_empty();
+                code.push(Self::add_index(is_initial_index, index));
+            }
+            &Term::Cons(..) => {
+                let is_initial_index = self.lists.is_empty();
+                self.lists.push(Self::add_index(is_initial_index, index));
+            }
+            &Term::Constant(_, ref constant) => {
+                self.intercept_overlapping_constant(constant, index);
+
+                let code = self.constants
+                    .entry(constant.clone())
+                    .or_insert(vec![]);
+
+                let is_initial_index = code.is_empty();
+                code.push(Self::add_index(is_initial_index, index));
+            }
+            _ => {}
+        };
+    }
+
+    fn second_level_index<Index>(
+        indices: IndexMap<Index, ThirdLevelIndex>,
+        prelude: &mut CodeDeque,
+    ) -> IndexMap<Index, IntIndex>
+    where
+        Index: Eq + Hash,
+    {
+        let mut index_locs = IndexMap::new();
+
+        for (key, mut code) in indices.into_iter() {
+            if code.len() > 1 {
+                index_locs.insert(key, IntIndex::Internal(prelude.len()));
+                Self::cap_choice_seq_with_trust(&mut code);
+                prelude.extend(code.into_iter().map(|code| Line::from(code)));
+            } else {
+                code.first().map(|i| {
+                    index_locs.insert(key, IntIndex::External(i.offset()));
+                });
+            }
+        }
+
+        index_locs
+    }
+
+    fn no_indices(&self) -> bool {
+        let no_constants = self.constants.is_empty();
+        let no_structures = self.structures.is_empty();
+        let no_lists = self.lists.is_empty();
+
+        no_constants && no_structures && no_lists
+    }
+
+    fn flatten_index<Index>(index: IndexMap<Index, IntIndex>, len: usize) -> IndexMap<Index, usize>
+    where
+        Index: Eq + Hash,
+    {
+        let mut flattened_index = IndexMap::new();
+
+        for (key, int_index) in index.into_iter() {
+            match int_index {
+                IntIndex::External(offset) => {
+                    flattened_index.insert(key, offset + len + 1);
+                }
+                IntIndex::Internal(offset) => {
+                    flattened_index.insert(key, offset + 1);
+                }
+                _ => {}
+            };
+        }
+
+        flattened_index
+    }
+
+    fn adjust_internal_index(index: IntIndex) -> IntIndex {
+        match index {
+            IntIndex::Internal(o) => IntIndex::Internal(o + 1),
+            IntIndex::External(o) => IntIndex::External(o),
+            _ => IntIndex::Fail,
+        }
+    }
+
+    fn switch_on_constant(
+        con_ind: IndexMap<Constant, ThirdLevelIndex>,
+        prelude: &mut CodeDeque,
+    ) -> IntIndex {
+        let con_ind = Self::second_level_index(con_ind, prelude);
+
+        if con_ind.len() > 1 {
+            let index = Self::flatten_index(con_ind, prelude.len());
+            let instr = IndexingInstruction::SwitchOnConstant(index.len(), index);
+
+            prelude.push_front(Line::from(instr));
+
+            IntIndex::Internal(1)
+        } else {
+            con_ind
+                .values()
+                .next()
+                .map(|index| Self::adjust_internal_index(*index))
+                .unwrap_or(IntIndex::Fail)
+        }
+    }
+
+    fn switch_on_structure(
+        str_ind: IndexMap<(ClauseName, usize), ThirdLevelIndex>,
+        prelude: &mut CodeDeque,
+    ) -> IntIndex {
+        let str_ind = Self::second_level_index(str_ind, prelude);
+
+        if str_ind.len() > 1 {
+            let index = Self::flatten_index(str_ind, prelude.len());
+            let instr = IndexingInstruction::SwitchOnStructure(index.len(), index);
+
+            prelude.push_front(Line::from(instr));
+
+            IntIndex::Internal(1)
+        } else {
+            str_ind
+                .values()
+                .next()
+                .map(|index| Self::adjust_internal_index(*index))
+                .unwrap_or(IntIndex::Fail)
+        }
+    }
+
+    fn switch_on_list(mut lists: ThirdLevelIndex, prelude: &mut CodeDeque) -> IntIndex {
+        if lists.len() > 1 {
+            Self::cap_choice_seq_with_trust(&mut lists);
+            prelude.extend(lists.into_iter().map(|i| Line::from(i)));
+            IntIndex::Internal(0)
+        } else {
+            lists
+                .first()
+                .map(|i| IntIndex::External(i.offset()))
+                .unwrap_or(IntIndex::Fail)
+        }
+    }
+
+    fn switch_on_str_offset_from(
+        str_loc: IntIndex,
+        prelude_len: usize,
+        con_loc: IntIndex,
+    ) -> usize {
+        match str_loc {
+            IntIndex::External(o) => o + prelude_len + 1,
+            IntIndex::Fail => 0,
+            IntIndex::Internal(_) => match con_loc {
+                IntIndex::Internal(_) => 2,
+                _ => 1,
+            },
+        }
+    }
+
+    fn switch_on_con_offset_from(con_loc: IntIndex, prelude_len: usize) -> usize {
+        match con_loc {
+            IntIndex::External(offset) => offset + prelude_len + 1,
+            IntIndex::Fail => 0,
+            IntIndex::Internal(offset) => offset,
+        }
+    }
+
+    fn switch_on_lst_offset_from(
+        lst_loc: IntIndex,
+        prelude_len: usize,
+    ) -> usize {
+        match lst_loc {
+            IntIndex::External(o) => o + prelude_len + 1,
+            IntIndex::Fail => 0,
+            IntIndex::Internal(_) => 1, // this internal is always 0.
+        }
+    }
+
+    pub fn add_indices(self, code: &mut Code, mut code_body: Code) {
+        if self.no_indices() {
+            *code = code_body;
+            return;
+        }
+
+        let mut prelude = VecDeque::new();
+
+        let lst_loc = Self::switch_on_list(self.lists, &mut prelude);
+        let str_loc = Self::switch_on_structure(self.structures, &mut prelude);
+        let con_loc = Self::switch_on_constant(self.constants, &mut prelude);
+
+        let prelude_length = prelude.len();
+
+        for (index, line) in prelude.iter_mut().enumerate() {
+            match line {
+                &mut Line::IndexedChoice(IndexedChoiceInstruction::Try(ref mut i)) |
+                &mut Line::IndexedChoice(IndexedChoiceInstruction::Retry(ref mut i)) |
+                &mut Line::IndexedChoice(IndexedChoiceInstruction::Trust(ref mut i)) => {
+                    *i += prelude_length - index;
+                }
+                _ => {
+                }
+            }
+        }
+
+        let str_loc = Self::switch_on_str_offset_from(str_loc, prelude.len(), con_loc);
+        let con_loc = Self::switch_on_con_offset_from(con_loc, prelude.len());
+        let lst_loc = Self::switch_on_lst_offset_from(lst_loc, prelude.len());
+
+        let switch_instr =
+            IndexingInstruction::SwitchOnTerm(prelude.len() + 1, con_loc, lst_loc, str_loc);
+
+        prelude.push_front(Line::from(switch_instr));
+
+        *code = Vec::from(prelude);
+        code.append(&mut code_body);
+    }
+}