Peg.JS：简单的 if..then..else 实现

问题描述

我正在尝试为简单的 if..then..else 语句和简单语句实现语法。

它应该能够解析如下语句：

if things are going fine
then
    things are supposed to be this way
    just go with it
else
    nothing new
How are you?

文档以一个决定（如果...那么...否则）开始，然后是一个简单的陈述。

到目前为止我的语法是这样的：

document = decision / simple_statement / !.

decision = i:if t:then e:(else)? document { return { if: { cond: i },then: t,else: e } }

if = 'if' s:statement nl { return s }
then = 'then' nl actions:indented_statements+ { return actions }
else = 'else' nl actions:indented_statements+ { return actions }
indented_statements = ss:(tab statement nl)+ { return ss.reduce(function(st,el) { return st.concat(el) },[]) }
statement = text:$(char+) { return text.trim() }

simple_statement = s:statement nl document { return { action: s } }

char = [^\n\r]
ws = [ \t]*
tab = [\t]+ { return '' }
nl = [\r\n]+

这将返回一个输出：

{
   "if": {
      "cond": "things are going fine"
   },"then": [
      [
         "","things are supposed to be this way",[
            "
"
         ],"","just go with it",[
            "
"
         ]
      ]
   ],"else": [
      [
         "","nothing new",[
            "
"
         ]
      ]
   ]
}

1。为什么 then 和 else 数组中有多余的空字符串和数组？我应该怎么做才能删除它们？

2. 为什么我的语法在决定后没有读取简单的语句？我应该怎么做才能让它读取和解析整个文档？

---

EDIT：我想我知道我为什么要获取数组了。我更改了语法以删除 indented_statements 中的重复。

document = decision / simple_statement / !.

decision = i:if t:then e:(else)? document { return { if: i,else: e } }

if = 'if' s:statement nl { return s }
then = 'then' nl actions:indented_statements+ { return actions }
else = 'else' nl actions:indented_statements+ { return actions }
indented_statements = tab s:statement nl { return s }
statement = text:$(char+) { return text.trim() }

simple_statement = s:statement nl document { return { action: s } }

char = [^\n\r]
ws = [ \t]*
tab = [\t]+ { return '' }
nl = [\r\n]+

解决方法

我想出了答案。我需要提供重复的第一条语句：

document = (decision / simple_statement)*