Remove let
from documentation
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@ -286,17 +286,20 @@ Examples of usage:
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.. code-block:: clj
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.. code-block:: clj
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=>(let [collection {}]
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=>(do
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... (setv collection {})
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... (assoc collection "Dog" "Bark")
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... (assoc collection "Dog" "Bark")
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... (print collection))
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... (print collection))
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{u'Dog': u'Bark'}
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{u'Dog': u'Bark'}
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=>(let [collection {}]
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=>(do
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... (setv collection {})
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... (assoc collection "Dog" "Bark" "Cat" "Meow")
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... (assoc collection "Dog" "Bark" "Cat" "Meow")
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... (print collection))
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... (print collection))
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{u'Cat': u'Meow', u'Dog': u'Bark'}
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{u'Cat': u'Meow', u'Dog': u'Bark'}
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=>(let [collection [1 2 3 4]]
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=>(do
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... (setv collection [1 2 3 4])
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... (assoc collection 2 None)
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... (assoc collection 2 None)
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... (print collection))
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... (print collection))
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[1, 2, None, 4]
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[1, 2, None, 4]
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@ -555,9 +558,9 @@ Parameters may have the following keywords in front of them:
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.. code-block:: clj
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.. code-block:: clj
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=> (defn zig-zag-sum [&rest numbers]
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=> (defn zig-zag-sum [&rest numbers]
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(let [odd-numbers (list-comp x [x numbers] (odd? x))
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(setv odd-numbers (list-comp x [x numbers] (odd? x))
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even-numbers (list-comp x [x numbers] (even? x))]
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even-numbers (list-comp x [x numbers] (even? x)))
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(- (sum odd-numbers) (sum even-numbers))))
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(- (sum odd-numbers) (sum even-numbers)))
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=> (zig-zag-sum)
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=> (zig-zag-sum)
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0
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0
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@ -578,10 +581,10 @@ Parameters may have the following keywords in front of them:
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.. code-block:: clj
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.. code-block:: clj
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=> (defn compare [a b &kwonly keyfn [reverse false]]
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=> (defn compare [a b &kwonly keyfn [reverse false]]
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... (let [result (keyfn a b)]
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... (setv result (keyfn a b))
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... (if (not reverse)
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... (if (not reverse)
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... result
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... result
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... (- result))))
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... (- result)))
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=> (apply compare ["lisp" "python"]
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=> (apply compare ["lisp" "python"]
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... {"keyfn" (fn [x y]
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... {"keyfn" (fn [x y]
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... (reduce - (map (fn [s] (ord (first s))) [x y])))})
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... (reduce - (map (fn [s] (ord (first s))) [x y])))})
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@ -932,8 +935,9 @@ list. Example usage:
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.. code-block:: clj
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.. code-block:: clj
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=> (let [animals {"dog" "bark" "cat" "meow"}
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=> (do
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... numbers ["zero" "one" "two" "three"]]
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... (setv animals {"dog" "bark" "cat" "meow"}
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... numbers ["zero" "one" "two" "three"])
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... (print (get animals "dog"))
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... (print (get animals "dog"))
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... (print (get numbers 2)))
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... (print (get numbers 2)))
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bark
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bark
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@ -1148,36 +1152,6 @@ last
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6
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6
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let
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---
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``let`` is used to create lexically scoped variables. They are created at the
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beginning of the ``let`` form and cease to exist after the form. The following
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example showcases this behaviour:
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.. code-block:: clj
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=> (let [x 5] (print x)
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... (let [x 6] (print x))
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... (print x))
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5
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6
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5
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The ``let`` macro takes two parameters: a vector defining *variables*
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and the *body* which gets executed. *variables* is a vector of
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variable and value pairs.
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Note that the variable assignments are executed one by one, from left to right.
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The following example takes advantage of this:
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.. code-block:: clj
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=> (let [x 5
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y (+ x 1)] (print x y))
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5 6
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list-comp
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list-comp
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---------
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---------
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@ -1209,30 +1183,20 @@ nonlocal
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``nonlocal`` can be used to mark a symbol as not local to the current scope.
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``nonlocal`` can be used to mark a symbol as not local to the current scope.
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The parameters are the names of symbols to mark as nonlocal. This is necessary
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The parameters are the names of symbols to mark as nonlocal. This is necessary
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to modify variables through nested ``let`` or ``fn`` scopes:
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to modify variables through nested ``fn`` scopes:
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.. code-block:: clj
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.. code-block:: clj
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(let [x 0]
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(for [y (range 10)]
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(let [z (inc y)]
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(nonlocal x) ; allow the setv to "jump scope" to resolve x
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(setv x (+ x y))))
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x)
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(defn some-function []
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(defn some-function []
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(let [x 0]
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(setv x 0)
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(register-some-callback
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(register-some-callback
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(fn [stuff]
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(fn [stuff]
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(nonlocal x)
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(nonlocal x)
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(setv x stuff)))))
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(setv x stuff))))
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In the first example, without the call to ``(nonlocal x)``, this code would
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Without the call to ``(nonlocal x)``, the inner function would redefine ``x`` to
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result in an UnboundLocalError being raised during the call to ``setv``.
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``stuff`` inside its local scope instead of overwriting the ``x`` in the outer
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function.
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In the second example, without the call to ``(nonlocal x)``, the inner function
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would redefine ``x`` to ``stuff`` inside its local scope instead of overwriting
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the ``x`` in the outer function
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See `PEP3104 <https://www.python.org/dev/peps/pep-3104/>`_ for further
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See `PEP3104 <https://www.python.org/dev/peps/pep-3104/>`_ for further
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information.
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information.
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@ -1698,9 +1662,10 @@ expands to:
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.. code-block:: hy
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.. code-block:: hy
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(let [a (gensym)
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(do
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(setv a (gensym)
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b (gensym)
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b (gensym)
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c (gensym)]
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c (gensym))
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...)
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...)
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.. seealso::
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.. seealso::
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@ -1203,10 +1203,9 @@ if *from-file* ends before a complete expression can be parsed.
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=> (with [f (open "example.hy")]
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=> (with [f (open "example.hy")]
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... (try
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... (try
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... (while True
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... (while True
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... (let [exp (read f)]
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... (setv exp (read f))
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... (do
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... (print "OHY" exp)
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... (print "OHY" exp)
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... (eval exp))))
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... (eval exp))
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... (except [e EOFError]
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... (except [e EOFError]
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... (print "EOF!"))))
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... (print "EOF!"))))
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OHY ('print' 'hello')
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OHY ('print' 'hello')
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@ -381,7 +381,8 @@ A first pass might be something like:
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.. code-block:: hy
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.. code-block:: hy
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(defmacro nif [expr pos-form zero-form neg-form]
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(defmacro nif [expr pos-form zero-form neg-form]
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`(let [obscure-name ~expr]
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`(do
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(setv obscure-name ~expr)
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(cond [(pos? obscure-name) ~pos-form]
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(cond [(pos? obscure-name) ~pos-form]
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[(zero? obscure-name) ~zero-form]
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[(zero? obscure-name) ~zero-form]
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[(neg? obscure-name) ~neg-form])))
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[(neg? obscure-name) ~neg-form])))
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@ -396,15 +397,16 @@ such an occasion. A much better version of ``nif`` would be:
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.. code-block:: hy
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.. code-block:: hy
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(defmacro nif [expr pos-form zero-form neg-form]
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(defmacro nif [expr pos-form zero-form neg-form]
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(let [g (gensym)]
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(setv g (gensym))
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`(let [~g ~expr]
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`(do
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(setv ~g ~expr)
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(cond [(pos? ~g) ~pos-form]
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(cond [(pos? ~g) ~pos-form]
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[(zero? ~g) ~zero-form]
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[(zero? ~g) ~zero-form]
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[(neg? ~g) ~neg-form]))))
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[(neg? ~g) ~neg-form])))
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This is an easy case, since there is only one symbol. But if there is
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This is an easy case, since there is only one symbol. But if there is
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a need for several gensym's there is a second macro :ref:`with-gensyms` that
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a need for several gensym's there is a second macro :ref:`with-gensyms` that
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basically expands to a series of ``let`` statements:
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basically expands to a ``setv`` form:
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.. code-block:: hy
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.. code-block:: hy
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@ -415,9 +417,10 @@ expands to:
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.. code-block:: hy
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.. code-block:: hy
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(let [a (gensym)
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(do
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(setv a (gensym)
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b (gensym)
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b (gensym)
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c (gensym)]
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c (gensym))
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...)
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...)
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so our re-written ``nif`` would look like:
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so our re-written ``nif`` would look like:
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@ -426,10 +429,10 @@ so our re-written ``nif`` would look like:
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(defmacro nif [expr pos-form zero-form neg-form]
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(defmacro nif [expr pos-form zero-form neg-form]
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(with-gensyms [g]
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(with-gensyms [g]
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`(let [~g ~expr]
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`(setv [~g ~expr])
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(cond [(pos? ~g) ~pos-form]
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`(cond [(pos? ~g) ~pos-form]
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[(zero? ~g) ~zero-form]
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[(zero? ~g) ~zero-form]
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[(neg? ~g) ~neg-form]))))
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[(neg? ~g) ~neg-form])))
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Finally, though we can make a new macro that does all this for us. :ref:`defmacro/g!`
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Finally, though we can make a new macro that does all this for us. :ref:`defmacro/g!`
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will take all symbols that begin with ``g!`` and automatically call ``gensym`` with the
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will take all symbols that begin with ``g!`` and automatically call ``gensym`` with the
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@ -440,10 +443,11 @@ Our final version of ``nif``, built with ``defmacro/g!`` becomes:
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.. code-block:: hy
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.. code-block:: hy
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(defmacro/g! nif [expr pos-form zero-form neg-form]
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(defmacro/g! nif [expr pos-form zero-form neg-form]
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`(let [~g!res ~expr]
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`(do
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(setv ~g!res ~expr)
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(cond [(pos? ~g!res) ~pos-form]
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(cond [(pos? ~g!res) ~pos-form]
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[(zero? ~g!res) ~zero-form]
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[(zero? ~g!res) ~zero-form]
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[(neg? ~g!res) ~neg-form]))))
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[(neg? ~g!res) ~neg-form])))
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@ -101,15 +101,6 @@ Layout & Indentation
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) ; GAH, BURN IT WITH FIRE
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) ; GAH, BURN IT WITH FIRE
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+ Vertically align ``let`` blocks.
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.. code-block:: clj
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(let [foo (bar)
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qux (baz)]
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(foo qux))
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+ Inline comments shall be two spaces from the end of the code; they
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+ Inline comments shall be two spaces from the end of the code; they
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must always have a space between the comment character and the start
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must always have a space between the comment character and the start
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of the comment. Also, try to not comment the obvious.
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of the comment. Also, try to not comment the obvious.
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@ -539,8 +539,8 @@ We can also manipulate code with macros:
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.. code-block:: clj
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.. code-block:: clj
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=> (defmacro rev [code]
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=> (defmacro rev [code]
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... (let [op (last code) params (list (butlast code))]
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... (setv op (last code) params (list (butlast code)))
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... `(~op ~@params)))
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... `(~op ~@params))
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=> (rev (1 2 3 +))
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=> (rev (1 2 3 +))
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6
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6
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@ -559,8 +559,8 @@ characters that soon):
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.. code-block:: clj
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.. code-block:: clj
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=> (defreader ↻ [code]
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=> (defreader ↻ [code]
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... (let [op (last code) params (list (butlast code))]
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... (setv op (last code) params (list (butlast code)))
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... `(~op ~@params)))
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... `(~op ~@params))
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=> #↻(1 2 3 +)
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=> #↻(1 2 3 +)
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6
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6
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