简约解析器-尝试解析分配语法时出错 [英] parsimonious parser - error trying to parse assignment grammar

问题描述

我正在使用 Python Parsimonious Parser 尝试为一种简单的语言构建解释器， m设计.我观看了教程视频，它非常有用，现在我正在慢慢修改代码符合我自己的规则.我陷入了最初定义为的分配规则:

I'm using the Python Parsimonious Parser to try to build an interpreter for a simple language I'm designing. I watched this tutorial video which was very helpful, and now I'm slowly modifying the code to match my own rules. I'm stuck on an assignment rule originally defined as:

def assignment(self, node, children):
    'assignment = lvalue "=" expr'
    lvalue, _, expr = children
    self.env[lvalue] = expr
    return expr

我使用以下语法对规则进行了一些修改:

I modified the rule slightly with the following grammar:

def assignment(self, node, children):
    'assignment = "SET" lvalue "," expr'
    _, lvalue, _, expr = children
    self.env[lvalue] = expr
    return expr

例如，我希望解析器对SET a, 7求值，与a = 7相同，并将值7绑定到名称a.但是，当我尝试解析它时，我从Parsimonious库中得到了这个错误:

I'd like the parser to evaluate SET a, 7 for example, the same as a = 7 and bind the value 7 to the name a. However, when I attempt to parse it, I get this error from the Parsimonious library:

parsimonious.exceptions.IncompleteParseError: Rule 'program' matched in its 
entirety, but it didn't consume all the text. The non-matching portion of 
the text begins with 'SET a, 7' (line 1, column 1).

我是解析/词法分析的新手，不确定我是否正确定义了规则.希望有人具有更多的解析/词法处理经验，可以帮助我正确地定义规则并解释我哪里出错了.也许还向我解释了简约错误?

I'm fairly new to parsing/lexing and am not entirely sure if I defined the rule correctly. Was hoping someone with more parsing/lexing experience can help me properly define the rule and explain where I went wrong. Also perhaps explain the Parsimonious error to me?

推荐答案

当我尝试解析SET a, 7时，我的lvalue规则未考虑SET和左值a之间的空格. .这是因为我将lvalue规则定义为'lvalue = ~"[A-Za-z]+" _'，该规则未考虑名称前的空格.我重新定义了分配规则，以说明GET和名称之间的空格:

When I was trying to parse SET a, 7, my lvalue rule did not take into account the whitespace between the SET and the lvalue a. This is because I defined my lvalue rule as 'lvalue = ~"[A-Za-z]+" _' which doesn't take into account whitespace before the name. I redefined my assignment rule as follows to account for whitespace between the GET and the name:

'setvar = "SETVAR" _ lvalue _ "," _ expr'

节俭似乎要好得多.

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