Add project, with basic functionality

Tokenises expressions
Prepares a truth table
Simulates the expression
Works with AND and OR, and variables
No ( ) or NOT support

Author: tomc128

.vscode/settings.json

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+{
+    "python.analysis.typeCheckingMode": "basic"
+}

boolean_expression_parser.py

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+TOKENS = {
+    'AND': 'AND',
+    '.': 'AND',
+    'OR': 'OR',
+    '+': 'OR',
+    'NOT': 'NOT',
+    '!': 'NOT',
+    '^': 'NOT',
+    '¬': 'NOT',
+    '(': 'OPEN_PAREN',
+    ')': 'CLOSE_PAREN',
+}
+
+OPERATORS = ['AND', 'OR', 'NOT']
+
+DEBUG_LOGGING = False
+
+
+Table = list[list[bool | None]]
+Expression = tuple[list[str], list[str]]
+
+
+def debug_print(*values):
+    if DEBUG_LOGGING:
+        print(*values)
+
+
+def print_table(expr: Expression, table: Table) -> None:
+    '''Prints a table in a nice format.'''
+
+    header = ' '.join(expr[1]) + ' | Result'
+    print(header)
+    print('-' * len(header))
+
+    for row in table:
+        print(' '.join([ ('1' if x else '0') for x in row[:-1] ]), '|', '1' if row[-1] else '0')
+
+
+
+def tokenise(text: str) -> Expression:
+    '''Converts a boolean expression string into a list of tokens.'''
+
+    tokens: list[str] = []
+    variables: list[str] = []
+    text = text.upper()
+
+    i: int = 0
+    while True:
+        if i >= len(text):
+            break
+
+        char = text[i]
+
+        if char == ' ':
+            i += 1
+            continue
+
+        if ' ' in text[i:]:
+            next_word_index = text.index(' ', i)
+        else:
+            next_word_index = len(text) - 1
+
+        word = text[i:next_word_index]
+
+        debug_print(f'{char} {next_word_index} {word}')
+
+        if word in TOKENS:
+            tokens.append(TOKENS[word])
+            i = next_word_index
+            continue
+
+        if char in TOKENS:
+            tokens.append(TOKENS[char])
+            i += 1
+            continue
+
+        if char not in variables:
+            variables.append(char)
+
+        tokens.append(f'VAR_{char}')
+
+        i += 1
+
+    variables.sort()
+
+    return tokens, variables
+
+
+
+def prepare_table(expr: Expression):
+    variables = { x[0]: 0 for x in expr[1] }
+
+    num_rows = 2 ** len(variables)
+    table: Table = []
+
+    for row in range(num_rows):
+        bin_str = bin(row)[2:].zfill(len(variables)) # Remove 0b prefix
+        table.append([ bool(int(x)) for x in bin_str ])
+        table[row].append(None)
+
+    return table
+
+
+
+def simulate(expr: Expression, table: Table):
+
+    tokens = expr[0]
+    variables = expr[1]
+
+    for row in table:
+        for i, token in enumerate(tokens):
+            if token in OPERATORS:
+                result: bool | None = None
+
+                match token:
+                    case 'AND':
+                        operand1_token = tokens[i - 1]
+                        operand2_token = tokens[i + 1]
+                        operand1 = row[variables.index(operand1_token.replace('VAR_', ''))]
+                        operand2 = row[variables.index(operand2_token.replace('VAR_', ''))]
+                        result = operand1 and operand2
+                    case 'OR':
+                        operand1_token = tokens[i - 1]
+                        operand2_token = tokens[i + 1]
+                        operand1 = row[variables.index(operand1_token.replace('VAR_', ''))]
+                        operand2 = row[variables.index(operand2_token.replace('VAR_', ''))]
+                        result = operand1 or operand2
+                    case 'NOT':
+                        operand1_token = tokens[i + 1]
+                        operand1 = row[variables.index(operand1_token.replace('VAR_', ''))]
+                        result = not operand1
+                
+                row[-1] = result
+
+    return table
+    
+
+
+
+
+def main():
+    '''Main program loop.'''
+
+    print('Basic information:')
+    print(' - inputs should be letters, case insensitive (i.e. a=A)')
+    print(' - allowed gates: AND (.), OR (+), NOT (!,¬,^)')
+    print(' - allowed punctuation: (, )')
+    print(' - enter \'q\' to quit')
+
+    stop = False
+    while not stop:
+
+        expr1 = tokenise('A AND B . C OR A')
+        debug_print(f'Tokens: {",".join(expr1[0])}')
+        debug_print(f'Variables: {",".join(expr1[1])}')
+
+        table1 = prepare_table(expr1)
+        table1 = simulate(expr1, table1)
+
+        print_table(expr1, table1)
+
+
+        stop = True
+
+
+
+if __name__ == '__main__':
+    main()

errors.py

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+class UnknownTokenError(Exception):
+    pass