Fix 'some' (first logical true value or nil)

docs/language/core.rst

@@ -654,21 +654,25 @@ some
 
 Usage: ``(some pred coll)``
 
-Return True if ``(pred x)`` is logical true for any ``x`` in ``coll``, otherwise False. Return False if ``coll`` is empty.
+Return the first logical true value of ``(pred x)`` for any ``x`` in
+``coll``, otherwise ``nil``. Return ``nil`` if ``coll`` is empty.
 
 .. code-block:: hy
 
    => (some even? [2 4 6])
    True
 
-   => (some even? [1 3 5])
+   => (nil? (some even? [1 3 5]))
-   False
-
-   => (some even? [1 3 6])
    True
 
-   => (some even? [])
+   => (nil? (some identity [0 "" []]))
-   False
+   True
+
+   => (some identity [0 "non-empty-string" []])
+   'non-empty-string'
+
+   => (nil? (some even? []))
+   True
 
 
 .. _string?-fn:

hy/core/language.hy

@@ -26,7 +26,7 @@
 (import itertools)
 (import functools)
 (import collections)
-(import sys) 
+(import sys)
 (import [hy._compat [long-type]]) ; long for python2, int for python3
 (import [hy.models.cons [HyCons]])
 (import [hy.lex [LexException PrematureEndOfInput tokenize]])
@@ -299,8 +299,8 @@
   (nth coll 1))
 
 (defn some [pred coll]
-  "Return true if (pred x) is logical true for any x in coll, else false"
+  "Return the first logical true value of (pred x) for any x in coll, else nil"
-  (any (map pred coll)))
+  (first (filter nil (map pred coll))))
 
 (defn string [x]
   "Cast x as current string implementation"
@@ -347,7 +347,7 @@
     (setv buff (+ buff inn))
     (try
       (def parsed (first (tokenize buff)))
-      (except [e [LexException PrematureEndOfInput IndexError]]) 
+      (except [e [LexException PrematureEndOfInput IndexError]])
       (else (if parsed (break)))))
     parsed)
 

tests/native_tests/core.hy

@@ -474,9 +474,16 @@
 (defn test-some []
   "NATIVE: testing the some function"
   (assert-true (some even? [2 4 6]))
-  (assert-false (some even? [1 3 5]))
+  (assert-nil (some even? [1 3 5]))
-  (assert-true (some even? [1 3 6]))
+  (assert-true (some even? [1 2 3]))
-  (assert-false (some even? [])))
+  (assert-nil (some even? []))
+  ; 0, "" (empty string) and [] (empty list) are all logical false
+  (assert-nil (some identity [0 "" []]))
+  ; non-empty string is logical true
+  (assert-equal (some identity [0 "this string is non-empty" []])
+                "this string is non-empty")
+  ; nil if collection is empty
+  (assert-nil (some even? [])))
 
 (defn test-string? []
   "NATIVE: testing string?"