From f448fcdb3319e74644d66c671c30c232d770615f Mon Sep 17 00:00:00 2001
From: Boutade <thegoofist@protonmail.com>
Date: Fri, 6 Mar 2020 13:33:23 -0600
Subject: added <<first combinator

---
 package.lisp  |  1 +
 parzival.lisp | 12 +++++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/package.lisp b/package.lisp
index ed0cee9..8b33dac 100644
--- a/package.lisp
+++ b/package.lisp
@@ -22,6 +22,7 @@
    #:<<bind
    #:<<let
    #:<<and
+   #:<<first
    #:<<ending
    #:<<sat
    #:<<~sat
diff --git a/parzival.lisp b/parzival.lisp
index 85a6632..35d6304 100644
--- a/parzival.lisp
+++ b/parzival.lisp
@@ -176,7 +176,7 @@ in then. If the parse fails the combinator else is run instead."
 
 
 (defun <<and (parser1 parser2 &rest parsers)
-  "Just like <<AND-THEN but where parse results are ignored. I.e. Applies each
+  "Just like <<BIND but where parse results are ignored. I.e. Applies each
    parser in sequence, ignoring any intermediate results. The result (<<AND P1
    P2 ... PN) is the result of PN."
   (if parsers
@@ -184,6 +184,16 @@ in then. If the parse fails the combinator else is run instead."
       (<<bind parser1 (returning parser2))))
 
 
+(defun <<first (parser other &rest others-still)
+  "A bit like <<AND in reverse. Returns the parse result of the first parser,
+   but only if the other parsers all succeed."
+  (<<bind parser
+          (lambda (first)
+            (apply #'<<and (append (list other)
+                                   others-still
+                                   (list (<<result first)))))))
+
+
 (defun <<ending (parser)
   "Creates a parser that succeeds if PARSER succeeds and the end of the input has been reached."
   (<<bind parser
-- 
cgit v1.2.3