重新编写解析表达式语法(PEG),而无需左递归 [英] Re-write Parsing Expression Grammar (PEG) without left recursion
本文介绍了重新编写解析表达式语法(PEG),而无需左递归的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
使用 https://github.com/JetBrains/Grammar-Kit 如何重写没有左递归的语法?
Using https://github.com/JetBrains/Grammar-Kit how to rewrite grammar without left recursion?
grammar ::= exprs
exprs::= (sum_expr (';')?)*
private sum_expr::= sum_expr_infix | sum_expr_prefix
sum_expr_infix ::= number sum_expr_prefix
left sum_expr_prefix::= op_plus number
private op_plus ::= '+'
number ::= float | integer
float ::= digit+ '.' digit*
integer ::= digit+
private digit ::=('0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9')
样本输入:
10+20+30.0;
10+20+30.0
答案应保持解析树属性,其中节点包含2/3个子元素:
Answer shall maintain parse tree property that nodes contain 2/3 children:
推荐答案
此问题朝着正确的方向发展: 解析布尔表达式而无需左手递归
this question lead in the right direction: Parsing boolean expression without left hand recursion
grammar ::= e*
e ::= math separator?
math ::= add
add ::=
mul op_plus math
| mul op_minus math
| mul
mul ::=
factorial op_mul mul
| factorial op_div mul
| factorial
factorial ::= term op_factorial space* | term
op_factorial ::= '!'
term ::= parentheses | space* number space*
parentheses ::= '(' math ')'
op_minus ::= '-'
op_plus ::= '+'
op_div ::= '/'
op_mul ::= '*'
number ::= float | integer
float ::= (digit+'.') digit*
integer ::=digit+
digit ::= '0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9'
space ::= ' ' | '\t'
separator ::= ';'
测试输入:
1!
3*2+1
3*2+1+3.0!
3*2+1 + 3.0!
1+1+(1+1)!
这篇关于重新编写解析表达式语法(PEG),而无需左递归的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
查看全文