TatSu grammar

tatsu.py

from pprint import pprint
from tatsu import parse

grammar = '''
@@grammar::Grammar

start = 'if' ['happens that'] expression ['then'] ['return'] ['error']$ ;

expression  = condition [and condition];
            
condition   = 
            | 'A is B'
            | 'B is C'
            | 'A = B'
            | 'B != C'
            | 'element A is B'
            | 'object C is not equal to D'
            ;


or = 'or';
and = 'and';
'''

code = '''
if
A is B
and
B is C
then error
'''

code2='''
if happens that
A = B
and
B != C
then return error
'''

code3='''
if
element A is B
and
object C is not equal to D
then error
'''

ast = parse(grammar, code)
pprint(ast, indent=2, width=20)

ast = parse(grammar, code2)
pprint(ast, indent=2, width=20)

ast = parse(grammar, code3)
pprint(ast, indent=2, width=20)