CompilerConstruction/interpreter.py at master · PriyaSelvan/CompilerConstruction · GitHub

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import sys
sys.path.insert(0,"../..")  # Add path to ply-2.8/

f=open(sys.argv[1],'r')

reserved = {
    'print' : 'PRINT',
}

tokens = [
    'NAME','NUMBER',
    ] + list(reserved.values())

# Each literal must be a single character
literals = ['=','+','-','*','/']

# Tokens defns
def t_NAME(t):
    r'[a-zA-Z_][a-zA-Z_0-9]*'
    t.type = reserved.get(t.value,'NAME')    # Check for reserved words
    return t

def t_NUMBER(t):
    r'\d+'
    t.value = int(t.value)
    return t

t_ignore = " \t"

def t_newline(t):
    r'\n+'
    t.lexer.lineno += t.value.count("\n")

def t_error(t):
    print("Illegal character '%s'" % t.value[0])
    t.lexer.skip(1)

# Build the lexer, and enable debugging
import ply.lex as lex
lex.lex(debug=1)

# Parsing rules
precedence = (
    ('left','+','-'),('left','+','-')
    )

# dictionary of names
names = { }

def p_statement_assign(p):
    'statement : NAME "=" expression'
    names[p[1]] = p[3]

def p_statement_expr(p):
    'statement : PRINT expression'
    print(p[2])

def p_expression_term(p):
    'expression : term'
    p[0]=p[1]
def p_expression_binop(p):
    'expression : expression "+" term'
    p[0] = p[1] + p[3]

def p_expression_binop2(p):
    'expression : expression "-" term'
    p[0] = p[1] - p[3]

def p_term_factor(p):
    'term : factor'
    p[0]=p[1]
def p_term_binop(p):
    'term : term "*" factor'
    p[0] = p[1] * p[3]

def p_term_binop2(p):
    'term : term "/" factor'
    p[0] = p[1] / p[3]


def p_factor_number(p):
    "factor : NUMBER"
    p[0] = p[1]

def p_factor_name(p):
    "factor : NAME"
    try:
        p[0] = names[p[1]]
    except LookupError:
        print("Undefined name '%s'" % p[1])
        p[0] = 0

def p_error(p):
    if p:
        print("Syntax error at '%s'" % p.value)
    else:
        print("Syntax error at EOF")

import ply.yacc as yacc
yacc.yacc()
inp=f.readlines()
for s in inp:
    yacc.parse(s)