[英]help creating peg.js parser
I am wanting to create the parser, and expression syntax in peg.js that would allow me to do these things 我想在peg.js中创建解析器和表达式语法,这将允许我做这些事情
basically I want to pass in a mask and have a number output. 基本上我想传递一个掩码并有一个数字输出。
the mask has these abilities. 面具有这些能力。
1) generate a random number between 0-9 (character n
for expression? ) 1)生成0-9之间的随机数(表达式的字符n
?)
2) generate a random number between x and y( (x,y) for expression?) 2)在x和y之间生成一个随机数((x,y)用于表达式?)
3) literal numbers are valid (hopefully nothing needed for expession?) 3)字面数字是有效的(希望没有任何需要的东西?)
4) repeat previous expression x times({x} for expression?) 4)重复前面的表达式x次(表达式为{x}?)
5) repeat previous expression between x and y times({x,y} for expression?) 5)重复x和y次之间的前一个表达式({x,y}表达式?)
so an example expression could be 所以一个例子表达式可能是
027n(5,9){4}n12{2,8}(2,4)
the proposed expression syntax above is only an example, it can change. 上面提出的表达式语法只是一个例子,它可以改变。
can anyone provide help in creating the parser for this in peg.js ? 任何人都可以在peg.js中为此创建解析器提供帮助吗?
The idea is to make it generate a JavaScript function, which when executed, will return a random string according to the mask. 我们的想法是让它生成一个JavaScript函数,该函数在执行时将根据掩码返回一个随机字符串。
A literal number is any character between 0 to 9, so make it generate a function that returns itself. 文字数字是介于0到9之间的任何字符,因此要生成一个返回自身的函数。
literal_number
= num:[0-9]
{ return function() {
return num;
}; }
Then n
is for a random number. 那么n
是一个随机数。 Again, this generates a function to return a random number. 同样,这会生成一个返回随机数的函数。 I added + ''
to convert it to a string before returning. 在返回之前,我添加了+ ''
将其转换为字符串。
random_number
= "n"
{ return function() {
return Math.floor(Math.random() * 10) + '';
}; }
In the (a,b)
syntax, a
and b
are numbers, so we need to make it parse and return a number. 在(a,b)
语法中, a
和b
是数字,因此我们需要对其进行解析并返回一个数字。 Using the declaration from the calculator example: 使用计算器示例中的声明:
number
= digits:[0-9]+ { return parseInt(digits.join(""), 10); }
Then we can move on to create a rule for (a,b)
syntax. 然后我们可以继续为(a,b)
语法创建规则。
random_number_between
= "(" a:number "," b:number ")"
{ return function() {
return a + Math.floor(Math.random() * (b - a + 1)) + ''
}; }
So, these 3 things (literal_number, random_number, random_number_between) combine into a single expression that generates a valid function. 因此,这三件事(literal_number,random_number,random_number_between)组合成一个生成有效函数的表达式。
single_expression
= random_number
/ random_number_between
/ literal_number
A single expression, followed by {n}
or {a,b}
forms a repeated expression. 单个表达式,后跟{n}
或{a,b}
形成重复表达式。 A single expression is also a repeated expression, repeated one time. 单个表达式也是重复表达式,重复一次。
The idea of a repeated expression is, given a function, return a function that calls the input function N times, collect the result, and return it. 重复表达式的思想是,给定一个函数,返回一个函数,该函数调用输入函数N次,收集结果并返回它。
repeated_expression
= ex:single_expression "{" n:number "}" {
return function() {
var result = '';
for (var i = 0; i < n; i ++) {
result += ex();
}
return result;
};
}
/ ex:single_expression "{" a:number "," b:number "}" {
return function() {
var result = '';
var n = a + Math.floor(Math.random() * (b - a + 1))
for (var i = 0; i < n; i ++) {
result += ex();
}
return result;
};
}
/ ex:single_expression
Finally, repeated expressions can be put next to each other to concatenate. 最后,重复的表达式可以彼此相邻以进行连接。
expression
= list:repeated_expression* {
return function() {
var result = '';
for (var i = 0; i < list.length; i ++) {
result += list[i]();
}
return result;
};
}
Finally, you need a starting point, which defines a mask. 最后,您需要一个定义遮罩的起点。 This final bit scans the expression which returns a generates a function, and call it. 最后一位扫描表达式,返回a生成一个函数,然后调用它。 Put the following at the top , and when you try it online, it will generate a string of numbers according to your mask. 将以下内容放在顶部 ,当您在线尝试时,它将根据您的掩码生成一串数字。
mask
= ex:expression
{ return ex() }
Example run: 027n(5,9){4}n12{2,8}(2,4)
gives 0271568891222224
. 实施例操作: 027n(5,9){4}n12{2,8}(2,4)
得到0271568891222224
。
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