Best practices for named arguments
TL;DR: I want to know best practices for designing functions with multiple
optional arguments.
Okay, so I'm working to build machine learning algorithms in Clojure, and
they tend to need many arguments. Being a long-time Ruby dev, I like to
provide sensible defaults for almost all potential arguments that the
functions take. However, there are some parameters that have to be explicit
(namely, the data).
To alleviate the pain here, I've started to experiment with named
arguments. So far, I've come up with something like the following:
(defn descend [xs ys args]
(let [defaults {:gradient-fn gradient
:cost-fn cost
:yield-fn println
:alpha 0.01
:iterations 1000
:thetas (matrix 0 (second (dim xs)) 1)}
options (merge defaults (apply hash-map args))
{:keys [gradient-fn cost-fn yield-fn thetas alpha iterations]}
options]
(do-the-algorithm-using-locally-bound-vars)))
It's a little wordy and could be extracted into a macro a la defnk (RIP
clojure.contrib.def), but it works.
However, if I then want to use method delegation for some algorithms, the
named argument endeavor gets trickier.
Say I have the same function in two namespaces. One is a general gradient
descent function, and the other is a specific gradient descent function
whose only role is to curry a named parameter into the general function.
I want to do something like the following:
(defn descend [xs ys args]
(optimization/descend xs ys (conj args :cost-fn cost)))
The problem, of course, is that if I want to delegate the args array to
another function, I have to destructure args first before passing it into
another function. In fact, if I ever have a delegating function like this
(where a partial apply isn't good enough), I can't pass args through to the
delegating function because it's automatically vectorized.
How do I splat vectors into parameter lists? (Should I be passing in
records/maps instead of named parameters?)
Thanks,
David
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Re: Best practices for named arguments
TL;DR: I want to know best practices for designing functions with multiple
optional arguments.
Use destructing:
(defn f [required {:keys [foo bar] :or {foo :default}}]
[required foo bar])
(f 3 :bar 1 :foo 2) ;= [3 2 1]
(f 3 :bar 1) ;= [3 :default 1]
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Re: Best practices for named arguments
Hi,
you can use destructuring to provide defaults. And you can easily curry in
options when passing things through.
(defn general-descend
[xy ys
{:keys [gradient-fn cost-fn yield-fn alpha iterations thetas]
:or {cost-fncost
yield-fn println
alpha 0.01
iterations 1000
thetas (matrix 0 (second (dim xs)) 1)}}]
...)
(defn special-descend
[xs ys options]
(apply general-descend xs ys :cost-fn cost options))
Kind regards
Meikel
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Re: Best practices for named arguments
I'm not sure you read the whole question. I want to know how to delegate
optional arguments to other functions with the same method signatures.
On Friday, June 15, 2012 12:04:00 AM UTC-7, Vinzent wrote:
TL;DR: I want to know best practices for designing functions with multiple
optional arguments.
Use destructing:
(defn f [required {:keys [foo bar] :or {foo :default}}]
[required foo bar])
(f 3 :bar 1 :foo 2) ;= [3 2 1]
(f 3 :bar 1) ;= [3 :default 1]
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Re: Best practices for named arguments
Ah I see, I didn't realize I could apply the general-descend algorithm to
both atoms and arrays to get a flattened list. Thanks!
On Friday, June 15, 2012 12:05:36 AM UTC-7, Meikel Brandmeyer (kotarak)
wrote:
Hi,
you can use destructuring to provide defaults. And you can easily curry in
options when passing things through.
(defn general-descend
[xy ys
{:keys [gradient-fn cost-fn yield-fn alpha iterations thetas]
:or {cost-fncost
yield-fn println
alpha 0.01
iterations 1000
thetas (matrix 0 (second (dim xs)) 1)}}]
...)
(defn special-descend
[xs ys options]
(apply general-descend xs ys :cost-fn cost options))
Kind regards
Meikel
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Re: Best practices for named arguments
I think the best is to use maps. It is rarly a good idea to have too many
arguments.
Am 15.06.2012 08:51 schrieb David Jacobs da...@wit.io:
TL;DR: I want to know best practices for designing functions with multiple
optional arguments.
Okay, so I'm working to build machine learning algorithms in Clojure, and
they tend to need many arguments. Being a long-time Ruby dev, I like to
provide sensible defaults for almost all potential arguments that the
functions take. However, there are some parameters that have to be explicit
(namely, the data).
To alleviate the pain here, I've started to experiment with named
arguments. So far, I've come up with something like the following:
(defn descend [xs ys args]
(let [defaults {:gradient-fn gradient
:cost-fn cost
:yield-fn println
:alpha 0.01
:iterations 1000
:thetas (matrix 0 (second (dim xs)) 1)}
options (merge defaults (apply hash-map args))
{:keys [gradient-fn cost-fn yield-fn thetas alpha iterations]}
options]
(do-the-algorithm-using-locally-bound-vars)))
It's a little wordy and could be extracted into a macro a la defnk (RIP
clojure.contrib.def), but it works.
However, if I then want to use method delegation for some algorithms, the
named argument endeavor gets trickier.
Say I have the same function in two namespaces. One is a general gradient
descent function, and the other is a specific gradient descent function
whose only role is to curry a named parameter into the general function.
I want to do something like the following:
(defn descend [xs ys args]
(optimization/descend xs ys (conj args :cost-fn cost)))
The problem, of course, is that if I want to delegate the args array to
another function, I have to destructure args first before passing it into
another function. In fact, if I ever have a delegating function like this
(where a partial apply isn't good enough), I can't pass args through to the
delegating function because it's automatically vectorized.
How do I splat vectors into parameter lists? (Should I be passing in
records/maps instead of named parameters?)
Thanks,
David
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Re: Best practices for named arguments
Hello David. I have a very similar scenario according to named parameters liker you. Therefore I have written the library clojure.options which can be found here: https://github.com/guv/clojure.options The latest version is also on clojars. Greetings, Gunnar -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
Re: Best practices for named arguments
Very cool, this is exactly what I wanted. Thanks. On Friday, June 15, 2012 7:27:05 AM UTC-7, Gunnar Völkel wrote: Hello David. I have a very similar scenario according to named parameters liker you. Therefore I have written the library clojure.options which can be found here: https://github.com/guv/clojure.options The latest version is also on clojars. Greetings, Gunnar -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
