Adding assoc-get utility.

lib/chibi/config.scm

@@ -112,6 +112,23 @@
 (define (alist? x)
   (and (list? x) (every pair? x)))
 
+;;> \subsubsubsection{\rawcode{(assoc-get alist key [equal? [default]])}}
+
+;;> Utility analogous to \scheme{conf-get} on a pure alist.  Returns
+;;> the value of the cell in \var{alist} whose car is \var{equal?} to
+;;> \var{key}, where the value is determined as the \var{cadr} if the
+;;> cell is a proper list of two elements and the \var{cdr} otherwise.
+;;> If no cell is found, returns \var{default}, or \scheme{#f} if
+;;> unspecified.
+
+(define (assoc-get alist key . o)
+  (cond
+   ((assoc key alist (or (and (pair? o) (car o)) equal?))
+    => (lambda (x)
+         (if (and (pair? (cdr x)) (null? (cddr x))) (cadr x) (cdr x))))
+   (else
+    (and (pair? o) (pair? (cdr o)) (cadr o)))))
+
 ;;> Returns just the base of \var{config} without any parent.
 
 (define (conf-head config)

lib/chibi/config.sld

@@ -3,7 +3,8 @@
   (export make-conf conf? conf-load conf-load-in-path conf-load-cascaded
           conf-verify conf-extend conf-append conf-set conf-unfold-key
           conf-get conf-get-list conf-get-cdr conf-get-multi
-          conf-specialize read-from-file conf-source conf-head conf-parent)
+          conf-specialize read-from-file conf-source conf-head conf-parent
+          assoc-get)
   (import (scheme base) (scheme read) (scheme write) (scheme file)
           (scheme time) (srfi 1))
   ;; This is only used for config verification, it's acceptable to