我試圖用pyparsing
解析形式函數調用:解析嵌套函數調用使用pyparsing
f(x, y)
這很容易。但由於它是一個遞歸下降解析器,因此它也應該很容易解析:
f(g(x), y)
這就是我無法得到的。這裏有一個熬濃例如:
from pyparsing import Forward, Word, alphas, alphanums, nums, ZeroOrMore, Literal
lparen = Literal("(")
rparen = Literal(")")
identifier = Word(alphas, alphanums + "_")
integer = Word(nums)
functor = identifier
# allow expression to be used recursively
expression = Forward()
arg = identifier | integer | expression
args = arg + ZeroOrMore("," + arg)
expression << functor + lparen + args + rparen
print expression.parseString("f(x, y)")
print expression.parseString("f(g(x), y)")
而這裏的輸出:
['f', '(', 'x', ',', 'y', ')']
Traceback (most recent call last):
File "tmp.py", line 14, in <module>
print expression.parseString("f(g(x), y)")
File "/usr/local/lib/python2.6/dist-packages/pyparsing-1.5.6-py2.6.egg/pyparsing.py", line 1032, in parseString
raise exc
pyparsing.ParseException: Expected ")" (at char 3), (line:1, col:4)
爲什麼我的解析器解釋內表達的仿函數作爲一個獨立的標識?
尼斯抓,@Jason! – PaulMcG 2012-04-17 08:36:09