Yaltik/hy
2
0
Fork 0
Code Pull Requests Releases Activity
187268c960
hy/docs/language/core.rst

719 lines
10 KiB
ReStructuredText
Raw Normal View History

Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
=================
Hy Core
=================
Core Functions
===============
.. _dec-fn:
dec
---
Usage: ``(dec x)``
Return one less than x. Equivalent to ``(- x 1)``.
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
Raises ``TypeError`` if ``(not (numeric? x))``.
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. code-block:: clojure
=> (dec 3)
2
=> (dec 0)
-1
=> (dec 12.3)
11.3
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
.. _emtpy?-fn:
empty?
------
Usage: ``(empty? coll)``
Return True if ``coll`` is empty, i.e. ``(= 0 (len coll))``.
.. code-block:: clojure
=> (empty? [])
True
=> (empty? "")
True
=> (empty? (, 1 2))
False
.. _float?-fn:
float?
-------
Usage: ``(float? x)``
Return True if x is a float.
.. code-block:: clojure
=> (float? 3.2)
True
=> (float? -2)
False
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. _even?-fn:
even?
-----
Usage: ``(even? x)``
Return True if x is even.
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
Raises ``TypeError`` if ``(not (numeric? x))``.
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. code-block:: clojure
=> (even? 2)
True
=> (even? 13)
False
=> (even? 0)
True
.. _inc-fn:
inc
---
Usage: ``(inc x)``
Return one more than x. Equivalent to ``(+ x 1)``.
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
Raises ``TypeError`` if ``(not (numeric? x))``.
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. code-block:: clojure
=> (inc 3)
4
=> (inc 0)
1
=> (inc 12.3)
13.3
.. _instance?-fn:
instance?
---------
Usage: ``(instance? CLASS x)``
Return True if x is an instance of CLASS.
.. code-block:: clojure
=> (instance? float 1.0)
True
=> (instance? int 7)
True
=> (instance? str (str "foo"))
True
=> (defclass TestClass [object])
=> (setv inst (TestClass))
=> (instance? TestClass inst)
True
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
.. _integer?-fn:
integer?
--------
Usage: ``(integer? x)``
Return True if x is an integer. For Python 2, this is
either ``int`` or ``long``. For Python 3, this is ``int``.
.. code-block:: clojure
=> (integer? 3)
True
=> (integer? -2.4)
False
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. _iterable?-fn:
iterable?
---------
Usage: ``(iterable? x)``
Return True if x is iterable. Iterable objects return a new iterator
when ``(iter x)`` is called. Contrast with :ref:`iterator?-fn`.
.. code-block:: clojure
=> ;; works for strings
=> (iterable? (str "abcde"))
True
=> ;; works for lists
=> (iterable? [1 2 3 4 5])
True
=> ;; works for tuples
=> (iterable? (, 1 2 3))
True
=> ;; works for dicts
=> (iterable? {:a 1 :b 2 :c 3})
True
=> ;; works for iterators/generators
=> (iterable? (repeat 3))
True
.. _iterator?-fn:
iterator?
---------
Usage: ``(iterator? x)``
Return True if x is an iterator. Iterators are objects that return
themselves as an iterator when ``(iter x)`` is called.
Contrast with :ref:`iterable?-fn`.
.. code-block:: clojure
=> ;; doesn't work for a list
=> (iterator? [1 2 3 4 5])
False
=> ;; but we can get an iter from the list
=> (iterator? (iter [1 2 3 4 5]))
True
=> ;; doesn't work for dict
=> (iterator? {:a 1 :b 2 :c 3})
False
=> ;; create an iterator from the dict
=> (iterator? (iter {:a 1 :b 2 :c 3}))
True
.. _neg?-fn:
neg?
----
Usage: ``(neg? x)``
Return True if x is less than zero (0).
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
Raises ``TypeError`` if ``(not (numeric? x))``.
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. code-block:: clojure
=> (neg? -2)
True
=> (neg? 3)
False
=> (neg? 0)
False
.. _none?-fn:
none?
-----
Usage: ``(none? x)``
Return True if x is None.
.. code-block:: clojure
=> (none? None)
True
=> (none? 0)
False
=> (setf x None)
=> (none? x)
True
=> ;; list.append always returns None
=> (none? (.append [1 2 3] 4))
True
.. _nth-fn:
nth
---
Usage: ``(nth coll n)``
Return the `nth` item in a collection, counting from 0. Unlike
``get``, ``nth`` works on both iterators and iterables. Returns ``None``
if the `n` is outside the range of `coll`.
.. code-block:: clojure
=> (nth [1 2 4 7] 1)
2
=> (nth [1 2 4 7] 3)
7
=> (none? (nth [1 2 4 7] 5))
True
=> (nth (take 3 (drop 2 [1 2 3 4 5 6])) 2))
5
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
.. _numeric?-fn:
numeric?
---------
Usage: ``(numeric? x)``
Return True if x is a numeric, as defined in the Python
numbers module class ``numbers.Number``.
.. code-block:: clojure
=> (numeric? -2)
True
=> (numeric? 3.2)
True
=> (numeric? "foo")
False
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. _odd?-fn:
odd?
----
Usage: ``(odd? x)``
Return True if x is odd.
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
Raises ``TypeError`` if ``(not (numeric? x))``.
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. code-block:: clojure
=> (odd? 13)
True
=> (odd? 2)
False
=> (odd? 0)
False
.. _pos?-fn:
pos?
----
Usage: ``(pos? x)``
Return True if x is greater than zero (0).
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
Raises ``TypeError`` if ``(not (numeric? x))``.
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. code-block:: clojure
=> (pos? 3)
True
=> (pos? -2)
False
=> (pos? 0)
False
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
.. _second-fn:
second
-------
Usage: ``(second coll)``
Return the second member of ``coll``. Equivalent to
``(get coll 1)``
.. code-block:: clojure
=> (second [0 1 2])
1
.. _string?-fn:
string?
-------
Usage: ``(string? x)``
Return True if x is a string.
.. code-block:: clojure
=> (string? "foo")
True
=> (string? -2)
False
One more commit to change the test for Python 2/3 to a macro Note that this can't use the macro in hy.core.macros so there is a local copy in language.hy
2013-09-04 02:41:11 +02:00
.. _zero?-fn:
zero?
----
Usage: ``(zero? x)``
Return True if x is zero (0).
.. code-block:: clojure
=> (zero? 3)
False
=> (zero? -2)
False
=> (zero? 0)
True
Add zero? predicate to check if an object is zero
2013-09-02 11:28:21 +02:00
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
Sequence Functions
=======================
Sequence functions can either create or operate on a potentially
infinite sequence without requiring the sequence be fully realized in
a list or similar container. They do this by returning a Python
iterator.
We can use the canonical infinite Fibonacci number generator
as an example of how to use some of these functions.
.. code-block:: clojure
(defn fib []
(setf a 0)
(setf b 1)
(while true
(yield a)
(setf (, a b) (, b (+ a b)))))
Note the ``(while true ...)`` loop. If we run this in the REPL,
.. code-block:: clojure
=> (fib)
<generator object fib at 0x101e642d0>
Calling the function only returns an iterator, but does no
work until we consume it. Trying something like this is not recommend as
the infinite loop will run until it consumes all available RAM, or
in this case until I killed it.
.. code-block:: clojure
=> (list (fib))
[1] 91474 killed hy
To get the first 10 Fibonacci numbers, use :ref:`take-fn`. Note that
:ref:`take-fn` also returns a generator, so I create a list from it.
.. code-block:: clojure
=> (list (take 10 (fib)))
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
To get the Fibonacci number at index 9, (starting from 0):
.. code-block:: clojure
=> (nth (fib) 9)
34
.. _cycle-fn:
cycle
------
Usage: ``(cycle coll)``
Return an infinite iterator of the members of coll.
.. code-block:: clj
=> (list (take 7 (cycle [1 2 3])))
[1, 2, 3, 1, 2, 3, 1]
=> (list (take 2 (cycle [1 2 3])))
[1, 2]
.. _distinct-fn:
distinct
--------
Usage: ``(distinct coll)``
Returns an iterator containing only the unique members in ``coll``.
.. code-block:: clojure
=> (list (distinct [ 1 2 3 4 3 5 2 ]))
[1, 2, 3, 4, 5]
=> (list (distinct []))
[]
=> (list (distinct (iter [ 1 2 3 4 3 5 2 ])))
[1, 2, 3, 4, 5]
.. _drop-fn:
drop
----
Usage: ``(drop n coll)``
Return an iterator, skipping the first ``n`` members of ``coll``
.. code-block:: clojure
=> (list (drop 2 [1 2 3 4 5]))
[3, 4, 5]
=> (list (drop 4 [1 2 3 4 5]))
[5]
=> (list (drop 0 [1 2 3 4 5]))
[1, 2, 3, 4, 5]
=> (list (drop 6 [1 2 3 4 5]))
[]
Second (smaller) set of native core functions This rounds out the first pass at a set of core functions, adding some that were not in the first PR. From here I'm working on a contrib.seq and contrib.io module to hold less obvious but maybe interesting native functions that can move to core if desired. This should also close out issure #150 asking for some core functions like these.
2013-07-29 18:40:48 +02:00
.. _drop-while-fn:
drop-while
-----------
Usage: ``(drop-while pred coll)``
Return an iterator, skipping members of ``coll`` until ``pred``
is False.
.. code-block:: clojure
=> (list (drop-while even? [2 4 7 8 9]))
[7, 8, 9]
=> (list (drop-while numeric? [1 2 3 None "a"])))
[None, u'a']
=> (list (drop-while pos? [2 4 7 8 9]))
[]
Add set of new core functions Add set of new core functions to the stdlib. Moved the auto-import code from compile_expression to HySymbol so that "even?' in this style expression will be found and imported. (list (filter even? [1 2 3 4 5])) The core functions are documented in 2 sections, one for basic functions like (even?..) and (nth ...) and one for all the sequence functions. Update: This removes all the caching decorators, misnamed as 'lazy-seq' from the core. All sequence methods now just use yield to return a generator, so they are Python-lazy Further refinements of core functions Cleaned up the docs to use 'iterator' instead of 'generator' Fixed drop to just return the iterator instead of an extra yield loop. But also added a test to catch dropping too many.
2013-07-08 04:36:26 +02:00
.. _filter-fn:
filter
------
Usage: ``(filter pred coll)``
Return an iterator for all items in ``coll`` that pass the predicate ``pred``.
See also :ref:`remove-fn`.
.. code-block:: clojure
=> (list (filter pos? [1 2 3 -4 5 -7]))
[1, 2, 3, 5]
=> (list (filter even? [1 2 3 -4 5 -7]))
[2, -4]
.. _iterate-fn:
iterate
-------
Usage: ``(iterate fn x)``
Return an iterator of `x`, `fn(x)`, `fn(fn(x))`.
.. code-block:: clojure
=> (list (take 5 (iterate inc 5)))
[5, 6, 7, 8, 9]
=> (list (take 5 (iterate (fn [x] (* x x)) 5)))
[5, 25, 625, 390625, 152587890625]
.. _remove-fn:
remove
------
Usage: ``(remove pred coll)``
Return an iterator from ``coll`` with elements that pass the
predicate, ``pred``, removed.
See also :ref:`filter-fn`.
.. code-block:: clojure
=> (list (remove odd? [1 2 3 4 5 6 7]))
[2, 4, 6]
=> (list (remove pos? [1 2 3 4 5 6 7]))
[]
=> (list (remove neg? [1 2 3 4 5 6 7]))
[1, 2, 3, 4, 5, 6, 7]
.. _repeat-fn:
repeat
------
Usage: ``(repeat x)``
Return an iterator (infinite) of ``x``.
.. code-block:: clojure
=> (list (take 6 (repeat "s")))
[u's', u's', u's', u's', u's', u's']
.. _repeatedly-fn:
repeatedly
----------
Usage: ``(repeatedly fn)``
Return an iterator by calling ``fn`` repeatedly.
.. code-block:: clojure
=> (import [random [randint]])
=> (list (take 5 (repeatedly (fn [] (randint 0 10)))))
[6, 2, 0, 6, 7]
.. _take-fn:
take
----
Usage: ``(take n coll)``
Return an iterator containing the first ``n`` members of ``coll``.
.. code-block:: clojure
=> (list (take 3 [1 2 3 4 5]))
[1, 2, 3]
=> (list (take 4 (repeat "s")))
[u's', u's', u's', u's']
=> (list (take 0 (repeat "s")))
[]
.. _take-nth-fn:
take-nth
--------
Usage: ``(take-nth n coll)``
Return an iterator containing every ``nth`` member of ``coll``.
.. code-block:: clojure
=> (list (take-nth 2 [1 2 3 4 5 6 7]))
[1, 3, 5, 7]
=> (list (take-nth 3 [1 2 3 4 5 6 7]))
[1, 4, 7]
=> (list (take-nth 4 [1 2 3 4 5 6 7]))
[1, 5]
=> (list (take-nth 10 [1 2 3 4 5 6 7]))
[1]
.. _take-while-fn:
take-while
----------
Usage: ``(take-while pred coll)``
Return an iterator from ``coll`` as long as predicate, ``pred`` returns True.
.. code-block:: clojure
=> (list (take-while pos? [ 1 2 3 -4 5]))
[1, 2, 3]
=> (list (take-while neg? [ -4 -3 1 2 5]))
[-4, -3]
=> (list (take-while neg? [ 1 2 3 -4 5]))
[]
Copy Permalink