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dsl_engine.py
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dsl_engine.py
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from pyparsing import alphas, alphanums, Word, Forward, nums, Optional, OneOrMore, Group, Regex, Combine, oneOf, Literal, QuotedString
from ast import ast_node, literal_value, tag_reference, assignment, arith, print_tags
class DSLEngine(object):
def __init__(self, context):
self._context = context
def to_assign(self, name, value):
return assignment.Assignment(name, value)
def to_literal(self, value):
return literal_value.LiteralValue(value)
def to_arith(self, left, oper, right):
return arith.Arith(left, oper, right)
def to_print_tags(self):
return print_tags.PrintTags()
def _build_grammar(self):
expr = Forward()
float_lit = Combine(Word(nums) + '.' + Word(nums))
float_lit.setName('float')
float_lit.setParseAction(lambda x: \
self.to_literal(float(x[0])))
int_lit = Word(nums)
int_lit.setName('int')
int_lit.setParseAction(lambda x: \
self.to_literal(int(x[0])))
num = (float_lit | int_lit)
num.setParseAction(lambda x: x[0])
tag_name = Word(alphas + "_", alphanums + "_")
tag_name.setName('tag_name')
tag_name.setParseAction(lambda t: tag_reference.TagReference(t[0]))
quoted_string = QuotedString("'")
quoted_string.setParseAction(lambda s: self.to_literal(s[0]))
oper = oneOf('+ * / -')
oper.setParseAction(lambda o: o[0])
lpar = Literal("(").suppress()
rpar = Literal(")").suppress()
arith = Group(lpar + expr + oper + expr + rpar)
arith.setParseAction(lambda t: \
self.to_arith(t[0][0], t[0][1], t[0][2]))
assign = tag_name + '=' + expr
assign.setName('assign')
assign.setParseAction(lambda x: self.to_assign(x[0],x[2]))
print_tags = Literal('?')
print_tags.setParseAction(lambda x: self.to_print_tags())
expr <<(arith|assign|tag_name|num|quoted_string|print_tags)
expr.setParseAction(lambda x: x[0])
return expr
def get_result(self, script):
grammar = self._build_grammar()
res = grammar.parseString(script)
return res
def execute(self, script):
res = self.get_result(script)
res[0].execute(self._context)
return res