K-user mailing list

[Ulrich Kühne <ulrichk AT informatik.uni-bremen.de>]

Hi,

I would like to give some meaning to the newline character '\n' like it 
is used in python, as a delimiter. Checking the examples in the K 
distribution, I think I know how to define the lexing rule. However, the 
K parser obviously has its own idea of what to do with newlines, so my 
definition does not work. Is there any way to use newline (or tab stops) 
as tokens without using an external parser?

I also looked into the k-python project, they are actually using an 
external parser, but I would very much like to avoid having to generate 
these crazy ASCII noise ASTs ;-)

Here is my first try for a K module using newlines (instead of semicolons):

module NEWLINE-SYNTAX
  syntax Newline ::= Lexer{[\n]+} // use newline as a delimiter
  syntax Newline -/- [\n]         // make it a maximum match

  syntax Exp ::= Int | Int "+" Int [strict,left]

  syntax Stmt ::= "var" Id
        | Id "=" Exp   [strict(2)]
        | Exp          [avoid]
  syntax Stmts ::= Stmt | Stmts Newline Stmts [right]
endmodule

module NEWLINE imports NEWLINE-SYNTAX
  syntax Val ::= Int
  syntax KResult ::= Val

  // heat up statements
  rule <k>S:Stmt Newline Rest => S ~> Rest</k> [structural]
endmodule


Running krun on a sample file leads to a syntax error, since the 
newlines have disappeared:

>$ cat test
var x
x = 1 + 2

>$ krun test
[Error] Critical: Parse error: Syntax error near unexpected character 'x'
    File: test
    Location: (2,1,2,1)

Any help is appreciated.

regards,
Ulrich