2016-09-19 research

New Shell Language: Proposed Grammar (Updated)

Not an LL grammar... yet

Basics

P : L  
L : statement  
  | statement L
statement : L;   
          | V;   
          | E;  
          | F; 

Variables

V : type $id
  | type $id = expr
  | $id = expr
type : string  
     | int  
     | bool  
     | float  
     | array

Expressions

expr : "str"
     | $id
     | *expr
     | num
     | E
     | F
     | { elements }
     | expr + expr
     | expr * expr
     | expr / expr
     | expr % expr
     | expr - expr
     | expr ^ expr
     | expr++
     | expr--

comp : expr != expr
     | expr == expr
     | expr >= expr
     | expr <= expr
     | expr < expr
     | expr > expr
     | expr && expr
     | expr || expr

Executions

E : pipeline 
pipeline : pipeline redirect commad 
         | command 
command : [ cmd ] 
redirect : <<
         | <
         | >>
         | <>
         | >
         | |
         | >&
         | >|
         | <&
         | ;
         | &

Functions

F : type $id( parameters ) body END
  | $id( parameters )
parameters : param
param : type $id, param 
      | epsilon
body : L body
  | return expr body
  | epsilon

Conditionals

F : cond 
  | loop
cond : IF 
     | SWITCH
IF : if ( comparison ) body cont END
cont : ELSE 
    | ELIF
    | epsilon
comparison : comp
           | expr
ELSE : else body
ELIF : else if ( comparison ) body cont
SWITCH : switch ( comparison ) CASE DEFAULT END
CASE : case ( expression ) body CASE 
     | epsilon
DEFAULT : default body

Loops

loop : WHILE 
     | FOR
FOR : for ( loop_conditional ) body END
WHILE : while ( loop_conditional ) body END

Notes

• Need to define basic unix/linux tokens? Some defined here, only PIPE, BG, RW in scanner. Need 2>, for example?
• Need to define language functions, like atoi?
• Changed the {} block construct to having END statements to be more intuitive

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