forward chaining first implementaion

Author: KarimAly12

propositional_logic_inference_algorithms/forward_chaining

@@ -0,0 +1,76 @@
+import re
+
+
+def find_symbols_in_kb(knowledge_base: list[str]) -> dict:
+    '''
+    '''
+    inferred = {}
+
+    for i in range(len(knowledge_base)):
+        symbols = re.findall(r'[a-zA-Z]', knowledge_base[i])
+        for symbol in symbols:
+            if symbol not in inferred:
+                inferred[symbol] = False
+
+    return inferred
+
+
+def number_of_symbols_in_premise(knowledge_base: list[str]) -> dict:
+
+    '''
+    '''
+
+    count = {}
+    for clause in knowledge_base:
+        if(len(clause) != 1):
+            index = clause.find("=>")
+            premise = clause[:index]
+            letters = ''.join(e for e in premise if e.isalpha())
+            count[premise] = len(letters)
+
+    return count
+
+
+def get_known_facts(knowledge_base: list[str]) -> list[str]:
+
+    '''
+    '''
+    facts = []
+    for clause in knowledge_base:
+        if len(clause) == 1:
+            facts.append(clause)
+
+    return facts
+
+
+
+
+def forward_chianing(knowledge_base: list[str], query:str) -> bool:
+
+    count = number_of_symbols_in_premise(knowledge_base)
+    inferred = find_symbols_in_kb(knowledge_base)
+    queue = get_known_facts(knowledge_base)
+
+    while(len(queue) > 0):
+        p = queue.pop()
+        if p == query: return True
+        if inferred[p] == False:
+            inferred[p] = True
+            for clause in knowledge_base:
+                index = clause.find("=>")
+                premise = clause[:index]
+                if p in premise:
+                    count[premise] -= 1
+                    if count[premise] == 0:
+                        queue.append(clause[-1])
+
+    return False
+
+
+
+if __name__ == "__main__":
+    
+    kb = ["p => q", "q => r", "r => p", "s => t", "u => v", "v => w", "w => u", "a", "b", "c" , "w" , "u&q=>r", "q"]
+
+    result = forward_chianing(kb, "t")
+    print(result)