finish parser for assignment

/*
 a=12
 a[0]=13
 a,b=13

 assignment-> var_name '=' var_value

 var_name->var_name ',' var_name
          | id
          | id list_s

 list_s->list_table list_s
       ->list_table

 var_value->expr,var_value
          ->expr

*/

./walley parse "a,b,c=12,14+5"

Begin to Analyze a,b,c=12,14+5
id:|a|:0:1
punctuation:|,|:1:2
id:|b|:2:3
punctuation:|,|:3:4
id:|c|:4:5
assignment_operator:|=|:5:6
num:|12|:6:8
punctuation:|,|:8:9
num:|14|:9:11
m_operator:|+|:11:12
num:|5|:12:13
length is 1 12
length is 1 14
length is 1 5

============
( assignment( =(id a)(num 12))( =(id b)( +(num 14)(num 5)))( =(id c)(
+(num 14)(num 5))))