From 704d96bb21ba1aaadb18d6c7b12fbd6da8554174 Mon Sep 17 00:00:00 2001
From: colin <colin@cicadas.surf>
Date: Sun, 9 Jul 2023 13:55:04 -0700
Subject: Add: nicer >> form called >>>

---
 hyperquirks.lisp | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

(limited to 'hyperquirks.lisp')

diff --git a/hyperquirks.lisp b/hyperquirks.lisp
index d64ce08..7b6da14 100644
--- a/hyperquirks.lisp
+++ b/hyperquirks.lisp
@@ -150,7 +150,18 @@ form. When they do, the value of the previous form is passed into all
 instances is substituted in.
 
 However, two different substitution variables CANNOT APPEAR in a
-single pipe form."
+single pipe form.
+
+This macro accepts additional syntax: the :? form standing on its own
+indicates the the next form shold be a predicate that, if it evaluates
+to NIL, causes an early exit, with failure state FAIL.  
+
+E.g.
+
+(>> (:fail :oh-no!)
+  (random 10)      ; start with a random number
+  :? evenp         ; exit with :oh-no! unless even
+  (+ 10 _))        ; add 10 and return."
   (let ((prefix
           (etypecase prefix
             (string prefix)
@@ -158,6 +169,7 @@ single pipe form."
     (labels ((var-p (v)
                "A variable is a symbol that starts with PREFIX"
                (and (symbolp v)
+                    (<= (length prefix) (length (symbol-name v)))
                     (string= prefix (symbol-name v) :end2 (length prefix))))
              (pipe-form-p (form)
                "A pipe form is either a symbol or a tree that contains
@@ -211,6 +223,10 @@ single pipe form."
       (list 'block block
             (reduce #'folder (escape-early-transform pipe-forms) :initial-value initform)))))
 
+
+(defmacro >>> (initform &rest pipe-forms)
+  `(>> () ,initform ,@pipe-forms))
+
 (defmacro binding-cond (&body clauses)
   "Like cond except the first form of every clause is a binding form
 alá IMPERATIVE. 
-- 
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