[KDB +/Q]:将q解析树解析为q表达式(字符串) [英] [KDB+/Q]: Deparse q parse tree into q expression (string)

问题描述

让我们将deparse ¹ 定义为对q的本机parse的逆操作，以便满足以下条件:

Let's define deparse¹ as inverse operation to q's native parse, so that the following holds:

q)aStringQExpression~deparse parse aStringQExpression
1b

问题

deparse函数的定义是什么，以便上述内容确实有效?

What's the definition of deparse function so that the above indeed works?

例如，在下面的更新表达式中，我们知道"a*0^b+c-d"表达式对应于(*;`a;(^;0;(+;`b;(-;`c;`d))))解析树:

For example, in the below update expression, we know that "a*0^b+c-d" expression corresponds to (*;`a;(^;0;(+;`b;(-;`c;`d)))) parse tree:

q)-3!parse "update col:a*0^b+c-d from t"
"(!;`t;();0b;(,`col)!,(*;`a;(^;0;(+;`b;(-;`c;`d)))))"

因此设想的deparse函数应返回:

So the envisaged deparse function should return:

q)deparse "(*;`a;(^;0;(+;`b;(-;`c;`d))))"
"a*0^b+c-d"
q)deparse "(!;`t;();0b;(,`col)!,(*;`a;(^;0;(+;`b;(-;`c;`d)))))"
"update col:a*0^b+c-d from t"

动机/背景/用例: 可以说，用人眼(从左到右)，内联表达式可以更快地 grok )，而不是深层嵌套的解析树.尽管在后台，我的代码正在以编程方式编辑解析树，但对于调试或表示而言，将生成的解析树方便地转换为内联表达式字符串很有用.

Motivation/Background/Use case: Inline expressions are arguably faster to grok by human eye (left-to-right) than deeply nested parse trees. Although in the background my code is editing the parse tree programatically, it is useful for debugging or presentation to conveniently convert that resulting parse tree into inline expression string.

_{¹ 此处描述的类似功能: http://adv-r.had.co.nz/Expressions.html#parsing-and-deparsing}

_{¹ Similar functionality described here: http://adv-r.had.co.nz/Expressions.html#parsing-and-deparsing}

推荐答案

此来自Github的unparse存储库解决了该问题.很棒:

This unparse repository from Github solves the problem. Amazing:

q).unparse.unparse parse "update col:a*0^b+c-d from t"
"update col:(a*(0^(b+(c-d)))) from t"

q).unparse.unparse parse "a*0^b+c-d"
"(a*(0^(b+(c-d))))"

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