1 files changed, 156 insertions, 0 deletions
diff --git a/monkey/prolog/util.py b/monkey/prolog/util.py
new file mode 100644
index 0000000..0ab3c8b
--- /dev/null
+++ b/monkey/prolog/util.py
@@ -0,0 +1,156 @@
+#!/usr/bin/python3
+
+import itertools
+import math
+import re
+
+from .lexer import lexer
+from util import Token
+
+def tokenize(text):
+    lexer.input(text)
+    return [Token(t.type, t.value, t.lexpos) for t in lexer]
+
+operators = set([
+    'FROM', 'IMPLIES', 'NOT',
+    'EQU', 'NEQU', 'EQ', 'NEQ', 'UNIV', 'IS', 'EQA', 'NEQA',
+    'LT', 'LE', 'GT', 'GE', 'LTL', 'LEL', 'GTL', 'GEL',
+    'PLUS', 'MINUS', 'STAR', 'DIV', 'IDIV', 'MOD',
+    'POW', 'SEMI'
+])
+def stringify(tokens):
+    def token_str(t):
+        if t.type in ('PERIOD', 'COMMA'):
+            return str(t) + ' '
+        if t.type in operators:
+            return ' ' + str(t) + ' '
+        return str(t)
+    return ''.join(map(token_str, tokens))
+
+# Yield the sequence of rules in [code].
+def split(code):
+    tokens = tokenize(code)
+    start = 0
+    for idx, token in enumerate(tokens):
+        if token.type == 'PERIOD' and idx - start > 1:
+            yield stringify(tokens[start:idx])
+            start = idx + 1
+
+# return a list of lines in 'code', and a list of rule indexes
+def decompose(code):
+    lines = []
+    rules = []
+    tokens = tokenize(code)
+    tokens.append(Token('EOF'))
+
+    line = []
+    parens = []
+    rule_start = 0
+    for t in tokens:
+        if t.type == 'SEMI':
+            if line != []:
+                lines.append(tuple(line))
+                line = []
+            lines.append((t,))
+            continue
+        if not parens:
+            if t.type in ('PERIOD', 'FROM', 'COMMA', 'EOF'):
+                if line != []:
+                    lines.append(tuple(line))
+                    line = []
+                if t.type in ('PERIOD', 'EOF') and rule_start < len(lines):
+                    rules.append((rule_start, len(lines)))
+                    rule_start = len(lines)
+                continue
+        if t.type in ('LPAREN', 'LBRACKET', 'LBRACE'):
+            parens.append(t.type)
+        elif parens:
+            if t.type == 'RPAREN' and parens[-1] == 'LPAREN':
+                parens.pop()
+            elif t.type == 'RBRACKET' and parens[-1] == 'LBRACKET':
+                parens.pop()
+            elif t.type == 'RBRACE' and parens[-1] == 'LBRACE':
+                parens.pop()
+        line.append(t)
+    return tuple(lines), tuple(rules)
+
+# pretty-print a list of rules
+def compose(lines, rules):
+    code = ''
+    for start, end in rules:
+        for i in range(start, end):
+            line = lines[i]
+            if i > start:
+                code += '  '
+            code += stringify(line)
+            if i == end-1:
+                code += '.\n'
+            elif i == start:
+                code += ' :-\n'
+            else:
+                if line and line[-1].type != 'SEMI' and lines[i+1][-1].type != 'SEMI':
+                    code += ','
+                code += '\n'
+    return code.strip()
+
+# standardize variable names in order of appearance
+def rename_vars(tokens, names={}):
+    # copy names so we don't fuck it up
+    names = {k: v for k, v in names.items()}
+    next_id = len(names)
+    for i in range(len(tokens)):
+        if tokens[i].type == 'PERIOD':
+            names.clear()
+            next_id = 0
+        elif tokens[i] == Token('VARIABLE', '_'):
+            tokens[i] = Token('VARIABLE', 'A' + str(next_id))
+            next_id += 1
+        elif tokens[i].type == 'VARIABLE':
+            cur_name = tokens[i].val
+            if cur_name not in names:
+                names[cur_name] = next_id
+                next_id += 1
+            tokens[i] = Token('VARIABLE', 'A' + str(names[cur_name]))
+    return names
+
+# transformation = before → after; applied on line which is part of rule
+# return mapping from formal vars in before+after to actual vars in rule
+# line and rule should of course not be normalized
+def map_vars(before, after, line, rule):
+    mapping = {}
+    new_index = 0
+    for i in range(len(before)):
+        if line[i].type == 'VARIABLE':
+            formal_name = before[i].val
+            if line[i].val != '_':
+                actual_name = line[i].val
+            else:
+                actual_name = 'New'+str(new_index)
+                new_index += 1
+            mapping[formal_name] = actual_name
+
+    remaining_formal = [t.val for t in after if t.type == 'VARIABLE' and t.val not in mapping.keys()]
+    remaining_actual = [t.val for t in rule if t.type == 'VARIABLE' and t.val != '_' and t.val not in mapping.values()]
+
+    while len(remaining_actual) < len(remaining_formal):
+        remaining_actual.append('New'+str(new_index))
+        new_index += 1
+
+    for i, formal_name in enumerate(remaining_formal):
+        mapping[formal_name] = remaining_actual[i]
+
+    return mapping
+
+# Basic sanity check.
+if __name__ == '__main__':
+    print(compose(*decompose('dup([H|T], [H1|T1]) :- dup(T1, T2). ')))
+
+    rule = tokenize('dup([H|T], [H1|T1]) :- dup(T1, T2). ')
+    line = tokenize('dup([H|T], [H1|T1]) :-')
+    before = tokenize("dup([A0|A1], [A2|A3])")
+    after = tokenize("dup([A0|A1], [A5, A4|A3])")
+    var_names = rename_vars(before)
+    rename_vars(after, var_names)
+
+    mapping = map_vars(before, after, line, rule)
+    print(mapping)