def parse_grammar(initial, terminals, non_terminals, productions):
"""
Parse grammar from plain text to CP format
"""
G = Grammar()
productions = productions.split('\n')
f['epsilon'] = G.Epsilon
f['EOF'] = G.EOF
f[initial] = G.NonTerminal(initial, True)
for terminal in terminals.split(' '):
f[terminal] = G.Terminal(terminal)
for non_terminal in non_terminals.split(' '):
if non_terminal != f[initial].Name:
f[non_terminal] = G.NonTerminal(non_terminal)
# Parsing productions
for production in productions:
if not production:
continue
parse_production(production, G)
if errors:
break
if errors:
return (-1, errors)
return (0, G)
def G5():
G = Grammar()
S = G.NonTerminal('S', True)
A = G.NonTerminal('A')
a = G.Terminal('a')
S %= S + A | A
A %= a
return G