Clojure newbie, here.
I'm trying to implement a TemporalAdjuster in Clojure. I have the following:
(ns pto-calculator.logic.pay-periods
(:require [java-time :as j]))
(def next-pay-period
(reify java.time.temporal.TemporalAdjuster
(adjustInto [this temporal]
(let [local-date (java.time.LocalDate/from temporal)
day-of-month (.getDayOfMonth local-date)]
(if (< 14 day-of-month)
(j/plus local-date (j/days (- 14 day-of-month)))
(j/adjust local-date :last-day-of-month))))))
(defn get-next-pay-period [date]
(j/adjust date next-pay-period))
And I call it like this:
(ns pto-calculator.core
(:require [pto-calculator.logic.pay-periods :as p]
[java-time :as j])
(:gen-class))
(defn -main
[& args]
(p/get-next-pay-period j/local-date))
Today is March 2nd, so I expect get-next-pay-period to return March 14th, however, I'm getting an exception instead:
Caused by: java.lang.ClassCastException: java_time.local$local_date cannot be cast to java.time.temporal.Temporal
at java_time.adjuster$adjust.invokeStatic(adjuster.clj:64)
at java_time.adjuster$adjust.doInvoke(adjuster.clj:40)
at clojure.lang.RestFn.invoke(RestFn.java:425)
at pto_calculator.logic.pay_periods$get_next_pay_period.invokeStatic(pay_periods.clj:19)
at pto_calculator.logic.pay_periods$get_next_pay_period.invoke(pay_periods.clj:18)
My confusion is this: (j/local-date) returns an instance of java.time.LocalDate, which is a Temporal (according to the docs). So why wouldn't this work?
I've also tried:
(defn get-next-pay-period [^java.time.temporal.Temporal date]
...
But in that case I get this error:
java_time.local$local_date cannot be cast to java.time.temporal.Temporal
Is there a difference between java_time.local$local_date and java.time.LocalDate?
You aren't invoking java-time/local-date in your core namespace. You are passing a function to get-next-pay-period.
Instead of:
(defn -main
[& args]
(p/get-next-pay-period j/local-date))
Try:
(defn -main
[& args]
(p/get-next-pay-period (j/local-date)))
Related
I would like a macro this-ns such that it returns the namespace of the location where it is being called. For instance, if I have this code
(ns nstest.main
(:require [nstest.core :as nstest]))
(defn ns-str [x]
(-> x (.getName) name))
(defn -main [& args]
(println "The ns according to *ns*:" (ns-str *ns*))
(println "The actual ns:" (ns-str (nstest/this-ns))))
I would expect that calling lein run would produce this output:
The ns according to *ns*: user
The actual ns: nstest.main
What I came up with as implementation was the following code:
(ns nstest.core)
(defmacro this-ns []
(let [s (gensym)]
`(do (def ~s)
(-> (var ~s)
(.ns)))))
It does seem to work, but it feels very hacky. Notably, in the above example it will expand to def being invoked inside the -main function which does not feel very clean.
My question: Is there a better way to implement this-ns to obtain the namespace where this-ns is called?
here is one more variant:
(defmacro this-ns []
`(->> (fn []) str (re-find #"^.*?(?=\$|$)") symbol find-ns))
the thing is the anonymous function is compiled to a class named something like
playground.core$_main$fn__181#27a0a5a2, so it starts with the name of the actual namespace the function gets compiled in.
Can't say it looks any less hacky, then your variant, still it avoids the side effect, introduced by def in your case.
Interesting question. I would never have guessed that your code would output user for the first println statement.
The problem is that only the Clojure compiler knows the name of an NS, and that is only when a source file is being compiled. This information is lost before any functions in the NS are called at runtime. That is why we get user from the code: apparently lein calls demo.core/-main from the user ns.
The only way to save the NS information so it is accessible at runtime (vs compile time) is to force an addition to the NS under a known name, as you did with your def in the macro. This is similar to Sean's trick (from Carcingenicate's link):
(def ^:private my-ns *ns*) ; need to paste this into *each* ns
The only other approach I could think of was to somehow get the Java call stack, so we could find out who called our "get-ns" function. Of course, Java provides a simple way to examine the call stack:
(ns demo.core
(:use tupelo.core)
(:require
[clojure.string :as str]))
(defn caller-ns-func []
(let [ex (RuntimeException. "dummy")
st (.getStackTrace ex)
class-names (mapv #(.getClassName %) st)
class-name-this (first class-names)
class-name-caller (first
(drop-while #(= class-name-this %)
class-names))
; class-name-caller is like "tst.demo.core$funky"
[ns-name fn-name] (str/split class-name-caller #"\$")]
(vals->map ns-name fn-name)))
and usage:
(ns tst.demo.core
(:use demo.core tupelo.core tupelo.test)
(:require
[clojure.string :as str]
[demo.core :as core]))
(defn funky [& args]
(spyx (core/caller-ns-func)))
(dotest
(funky))
with result:
(core/caller-ns-func) => {:ns-name "tst.demo.core", :fn-name "funky"}
And we didn't even need a macro!
Here's a simple re-frame app that I tried to create based on the existing example project in re-frame's github repo. But it is only displaying things from the html file. Seems like no event is being dispatched. Can anyone point out what am I doing wrong? Thanks.
(ns simple.core
(:require [reagent.core :as reagent]
[re-frame.core :as rf]
[clojure.string :as str]))
(rf/reg-event-db
:rand
(fn [db [_ _]]
(assoc db :winner ( + 2 (rand-int 3)))))
(rf/reg-sub
:winner
(fn [db _]
(:winner db)))
(def participants ["Alice" "Bob" "Ellie"])
(defn winners-name
[idx]
(get participants idx))
(defn show-winner
[]
[:h1
(winners-name
(#(rf/subscribe [:winner])))])
(defn ui
[]
[:div
[:h1 "Lottery"]
[show-winner]])
(defn ^:export run
[]
(rf/dispatch-sync [:rand])
(reagent/render [ui]
(js/document.getElementById "app")))
The :rand handler will produce nil most times since you are adding 2 to the generated value and the participants vector only has 3 entries.
The issue is caused because of a pair of extra parenthesis around the deref thing. So the function winners-name is treating it as a list instead of an integer.
(winners-name
(#(rf/subscribe [:winner]))
EDIT: Turned out I was using require instead of :require in the namespace declaration. With :require, tools.namespace refreshes the logging namespace, and the problem goes away. I still find it curious, however, that the expression (eval `(var ~(symbol "A/func"))) does not work in the situation described below (that is, if B below is not refreshed).
Summary: I'm using tools.namespace. If I have namespaces A and B, and in B do (eval `(var ~(symbol "A/func"))), and (tools.namespace/refresh) and run the code, that works. But if I make a change to A, do (tools.namespace/refresh), so that only A refreshes, then running that expression gives the error: Cannot resolve var: A/func in this context, even though A/func exists. Why?
Longer version:
In my project, I have a logging module/namespace that uses robert-hooke (see below). I'm using tools.namespace to reload my code when I make changes.
The problem is the following: When I want to log (my logging currently just prints) something, I list the functions that I want to log in my logging namespace and do (t.n/refresh). That works. But if I make changes to the the namespaces that contain the functions that I want to log, and do (t.n/refresh) without making changes to the logging namespace, the logging no longer works (for the functions that have been refreshed). As soon as I make a change to logging, so that it too is refreshed by tools.namespace, it starts working again.
So, it's like the vars in namespaces that have been refreshed don't properly get their logging hooks. But I don't understand why.
Below is my logging namespace. I call add-logging-wrappers each time I run my program.
If I add (eval `(var ~(symbol "sv/register-damage"))) inside add-logging-wrappers, that's fine when logging has just been refreshed and the logging works. But those times the logging does not work, that expression causes the error Cannot resolve var: sv/register-damage in this context.
(ns game.logging
(require [robert.hooke :as rh]
[clojure.pprint :as pp]
[game.server.core :as sv]
[game.client.core :as cl]
[game.math :as math]
(game.common [core-functions :as ccfns]
[graphics :as gfx])
(game.server [pathfinding :as pf]))
(:use [game.utils]))
(defn log-println [name type object]
(println (str (current-thread-name) " // " name " " type ":\n"
(with-out-str
(pp/pprint object)))))
(defn print-output [name f & args]
(let [result (apply f args)]
(log-println name "output" result)
result))
(defn print-input [name f & args]
(log-println name "input" args)
(apply f args))
(defn print-call [name f & args]
(println (str (current-thread-name) "//" name))
(apply f args))
(defmacro make-name-var-list [fn-list]
`[~#(for [fn fn-list]
[(str fn) `(var ~fn)])])
(defmacro defloglist [name & fns]
`(def ~name (make-name-var-list [~#fns])))
(defn add-hooks [name-vars & wrappers]
(when (seq wrappers)
(doseq [[name var] name-vars]
(rh/add-hook var (partial (first wrappers) name)))
(recur name-vars (next wrappers))))
(defn get-ns-name-vars [ns-sym]
(-> (the-ns ns-sym) (#(.name %)) ns-interns))
(defn add-hooks-to-ns [ns-sym & wrappers]
(apply add-hooks (get-ns-name-vars ns-sym) wrappers))
(defloglist log-both
sv/distribute-exp ;; <--- things to log
sv/register-damage
sv/give-exp)
(defloglist log-input)
(defloglist log-output)
(defn add-logging-wrappers []
(dorun (->> (all-ns) (map #(.name %)) (mapcat ns-interns) (map second)
(map rh/clear-hooks)))
(add-hooks log-both print-output print-input)
(add-hooks log-input print-input)
(add-hooks log-output print-output))
I have the following clojure code (trying to write / get entries from redis):
(ns hello.core2)
(ns h hello.core2 (:require [taoensso.carmine :as car]))
(def pool (car/make-conn-pool))
(def spec-server1 (car/make-conn-spec))
(defmacro wcar [& body] `(car/with-conn pool spec-server1 ~#body))`
(defn -main
(wcar (car/ping)
(car/set "foo" "bar")
(car/get "foo")))
I get the following error:
Exception in thread "main" java.lang.IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol
at clojure.lang.RT.seqFrom(RT.java:487)
at clojure.lang.RT.seq(RT.java:468)
Any idea what im doing wrong?
(defn -main ...): you forgot the argument vector for the function -main; it should be (defn -main [& args] ...).
The problem is probably this:
(ns h hello.core2 (:require [taoensso.carmine :as car]))
There should be only one namespace declaration, like this (so also move the first ns expression):
(ns hello.core2
(:require [taoensso.carmine :as car]))
two files
types.clj:
(ns test.types)
(defrecord Price [date price])
(defrecord ProductPrice [name prices])
core.clj (It's OK)
(ns test.core
(:use [test.types])
(:use [clojure.string :only (split)]))
(defn read-data [file]
(let [name (subs (.getName file) 0 4)]
(with-open [rdr (clojure.java.io/reader file)]
(doall (map #(apply ->Price (split % #"\t")) (drop 2 (line-seq rdr)))))))
core.clj (java.lang.IllegalArgumentException: Unable to resolve classname: ProductPrice)
(ns test.core
(:use [test.types])
(:use [clojure.string :only (split)]))
(defn read-data [file]
(let [name (subs (.getName file) 0 4)]
(with-open [rdr (clojure.java.io/reader file)]
(ProductPrice. name (doall (map #(apply ->Price (split % #"\t")) (drop 2 (line-seq rdr))))))))
core.clj (It's OK)
(ns test.core
(:use [test.types])
(:use [clojure.string :only (split)]))
(defrecord tProductPrice [name prices])
(defn read-data [file]
(let [name (subs (.getName file) 0 4)]
(with-open [rdr (clojure.java.io/reader file)]
(tProductPrice. name (doall (map #(apply ->Price (split % #"\t")) (drop 2 (line-seq rdr)))))))
core.clj (java.lang.IllegalStateException: ->ProductPrice already refers to: #'test.types/->ProductPrice in namespace: test.core)
(ns test.core
(:use [test.types])
(:use [clojure.string :only (split)]))
(defrecord ProductPrice [name prices])
(defn read-data [file]
(let [name (subs (.getName file) 0 4)]
(with-open [rdr (clojure.java.io/reader file)]
(ProductPrice. name (doall (map #(apply ->Price (split % #"\t")) (drop 2 (line-seq rdr)))))))
I totally confused about these exceptions. And I can't find any more usage about 'record' except some simplest examples from clojure.org and books.
Any help, Thank you very much!
defrecord creates a java class in the package named after the current namespace. (ProductPrice. ...) is a call to the constructor of that type; this is java interop - not a plain function call.
You cannot refer to a class defined outside of java.lang or the current namespace unless you explicitly import it or specify the full package name. This includes calling its constructor.
So, to fix the problem you need to import Price and ProductPrice.
(ns test.core (:import [test.types Price]))
(Price. ...)
or call the full class+package name:
(test.types.Price. ...)