Fling, an S-Expression grepping tool

Berke Durak berke.durak@gmail.com

Purpose

This tool is used to select parts of S-Expressions, especially those generated automatically by Sexplib.

Example

Let's say you have the following type:

type entry =
  | Account of account
  | Closed of string
and account =
  {
    holder  : string;
    balance : float;
    opened  : string; (* A date *)
  }

Then Sexplib would serialize a sequence of entries as:

(Account ((holder Dupont) (balance 1234.5)))
(Account ((holder Durant) (balance 2345.6)))
(Closed  Dumont)
(Account ((holder Dupond) (balance 3456.7)))

If you want to select all the holder names and dates from such a sequence you can use

fling "(Tag Account (Seq ((Fields (holder opened) Emit) Newline)))" \
  examples/entries.sexp

Expression

An expression is either:

• A sequence of expressions (Seq (expr1 expr2 ... ))
• An Emit statement
• A Newline statement
• A constant string (Const "foo")
• A tag selector (Tag tag expr)
• A field selector (Fields (field1 field2 ...) expr)

Compilation

oasis setup && ./configure && make && make install