Added a module for (pre-post-order) utilities

Makefile

@@ -1,6 +1,6 @@
 TARGET := $(shell guile -c "(display (%site-dir))")
 CCACHE := $(shell guile -c "(display(%site-ccache-dir))")
-OBJ := csv.go
+OBJ := csv.go transform.scm
 
 .PHONY: all clean install uninstall
 all: $(OBJ)

csv/csv.scm

@@ -1,7 +1,8 @@
 ;; guile-csv
-;; Copyright (C) 2008, 2012, 2013 
+;; Copyright (C) 2008, 2012, 2013, 2021 
 ;; Andy Wingo <wingo at pobox dot com>
 ;; Nala Ginrut <nalaginrut@gmail.com>
+;; Brady McDonough
 
 ;; This program is free software; you can redistribute it and/or modify
 ;; it under the terms of the GNU Lesser General Public License as

csv/transform.scm

@@ -0,0 +1,45 @@
+;; guile-csv transform
+;; Copyright (C) 2021
+;; Brady McDonough
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU Lesser General Public License as
+;; published by the Free Software Foundation; either version 3 of the
+;; License, or (at your option) any later version.
+;;
+;; This program is distributed in the hope that it will be useful, but
+;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+;; Lesser General Public License for more details.
+;;
+;; You should have received a copy of the GNU Lesser General Public
+;; License along with this program; if not, contact:
+;;
+;; Free Software Foundation, Inc.     Voice:  +1-617-542-5942
+;; 51 Franklin Street, Fifth Floor    Fax:    +1-617-542-2652
+;; Boston, MA  02110-1301,  USA       gnu@gnu.org
+
+(define-module (csv transform)
+  #:use-module (ice-9 receive)
+  #:use-module (sxml transform)
+  #:export (bubble-term)
+  #:reexport (pre-post-order))
+
+(define (key-contains-defer str)
+  (lambda ($pair) (string-contains (symbol->string (car $pair)) str)))
+
+;; Generates a handler for pre-post-order.
+;; EXAMPLE USAGE:
+;; (pre-post-order $tree `(,(bubble-term rec "key-name")
+;;                         (*default* . ,(lambda x x))))
+;; This will generate a rule which travels in *preorder* to each record named
+;;'rec' and replace the rec symbol with the pair keyed as "key-name"
+(define-syntax bubble-term
+  (syntax-rules ()
+    ((_ record-sym $str)
+     `(record-sym *preorder* .
+                  ,(lambda $record
+                     (let* (($lst (cadr $record)))
+                       (receive (head rest)
+                           (partition (key-contains-defer $str) $lst)
+                         (cons head (cons rest '())))))))))