Miscellaneous functions

Uncategorized

This page references all other functions that don't fit in the previous categories. Over time, they might be moved to a different or new category.

->

Groups multiple shards together (as if they were a single shard). Also called shard-container.

This is useful for cases where you need multiple shards (to transform your data) but is allowed to have only one: for example, as the return value of a function (see function print-messages below).

CodeResult

(defn print-messages []
    (-> 
        (Msg "Hello World!")
        (Msg "Hello Universe!")
    ))

[info] [2022-07-06 14:14:43.056] [T-2168] [logging.cpp::98] [main] Hello World!
[info] [2022-07-06 14:14:43.058] [T-2168] [logging.cpp::98] [main] Hello Universe! 

apply

(apply f args) (apply f x args) (apply f x y args) (apply f x y z args)(apply f a b c d & args)

Applies fn f to the argument list formed by prepending intervening arguments to args.

(apply str ["cherry " "banana " "apple"])
;;=> "cherry banana apple"

(apply str "cherry " ["banana " "apple"])
;;=> "cherry banana apple"

(apply str "cherry " "banana " ["apple"])
;;=> "cherry banana apple"

(apply str "cherry " "banana " "apple" [])
;;=> "cherry banana apple"

atom

(atom x)

Creates and returns an Atom with an initial value of x and zero or more options (in any order). An Atom is a data type in Clojure that provides a way to manage shared, synchronous, independent state. An atom is just like any reference type in any other programming language.

;; Create new atom
(def my-atom (atom 0))

;; value under 'my-atom' to be replaced with incremented version
(swap! my-atom inc)
;;=> 1

deref

(deref ref)

Returns the most current state of the atom.

(deref (atom [1 2]))
;;=> [1 2]

fn?

(fn? f)

Return true if f is a function.

(fn? String.Join)
;;=> true

hex

(hex number)

Returns a hexadecimal representation for an input number.

(hex 2)
;;=> "0x0000000000000002"

keyword

(keyword s)

Returns a keyword with a given s string. Do not use : in the keyword strings, it will be added automatically.

(keyword "foo/bar")
;;=> :foo/bar

macro?

(macro? value)

Checks if a value is a macro.

(macro? defn)
;;=> true

meta

read-string

(read-string s)

Reads one object from the string s.

(read-string "2.3") ;;=> 2.300000

(read-string "(+ 1 1)") ;;=> (+ 1 1)

readline

(readline prompt)

Reads a line from stdin and returns it. Accepts prompt string.

(readline "Enter a line: ")

reset!

(reset! atom newval)

Sets the value of the atom to newval without regard for the current value. Returns newval.

(reset! (atom "apple") "mango")

run

Executes all the wires that have been scheduled on a given mesh.

(run <params>) takes two arguments: name of the mesh, and mesh iteration interval (no. of seconds between two mesh iterations).

An optional 3rd argument defines the maximum mesh iterations to run. This argument is a debug parameter - do not use it for production.

CodeResult

;; define a mesh (main)
(defmesh main)
;; define a looped wire
(defloop wire-hi
    (Msg "Hello World!"))
;; define a non-looped wire
(defwire wire-bye
    (Msg "Goodbye World"))
;; schedule both the wires on this mesh
(schedule main wire-hi)
(schedule main wire-bye)
;; run the mesh to execute scheduled wires
;; time between mesh iterations - 0.02 secs
;; max mesh iterations allowed - 5
(run main 0.02 5)
;; The last two args  may also be passed as mathematical expressions
;; (run main (/ 1 50) (+ 2 3))

[info] [2022-03-07 21:42:12.324] [T-18096] [logging.cpp::94] [wire-hi] Hello World!
[info] [2022-03-07 21:42:12.325] [T-18096] [logging.cpp::94] [wire-bye] Goodbye World
[info] [2022-03-07 21:42:12.351] [T-18096] [logging.cpp::94] [wire-hi] Hello World!
[info] [2022-03-07 21:42:12.367] [T-18096] [logging.cpp::94] [wire-hi] Hello World!
[info] [2022-03-07 21:42:12.397] [T-18096] [logging.cpp::94] [wire-hi] Hello World!
[info] [2022-03-07 21:42:12.413] [T-18096] [logging.cpp::94] [wire-hi] Hello World!

schedule

Queues a wire for execution on a given mesh.

Multiple wires can be scheduled on the same mesh. When a mesh is run, all the wires on it are executed.

CodeResult

;; define a mesh (main)
(defmesh main)
;; define a looped wire
(defloop wire-hi
    (Msg "Hello World!"))
;; define a non-looped wire
(defwire wire-bye
    (Msg "Goodbye World"))
;; schedule both the wires on this mesh
(schedule main wire-hi)
(schedule main wire-bye)
;; run all the scheduled wires on this mesh (main)
(run main)

[info] [2022-03-07 21:42:12.324] [T-18096] [logging.cpp::94] [wire-hi] Hello World!
[info] [2022-03-07 21:42:12.325] [T-18096] [logging.cpp::94] [wire-bye] Goodbye World
[info] [2022-03-07 21:42:12.351] [T-18096] [logging.cpp::94] [wire-hi] Hello World!
[info] [2022-03-07 21:42:12.367] [T-18096] [logging.cpp::94] [wire-hi] Hello World!
[info] [2022-03-07 21:42:12.397] [T-18096] [logging.cpp::94] [wire-hi] Hello World!
[info] [2022-03-07 21:42:12.413] [T-18096] [logging.cpp::94] [wire-hi] Hello World!

swap!

(swap! atom f) (swap! atom f x) (swap! atom f x y) (swap! atom f x y & args)

Atomically swaps the value of atom to be: (apply f current-value-of-atom args). Returns the value that was swapped in.

(swap! (atom []) conj "banana")
;;=> ["banana"]

symbol

(symbol name)

Convert string name to a symbol.

(symbol "apple")
;;=> apple

throw

Throws Error using input argument as an error message.

(throw "This is an error..")
;; Error: "This is an error.." Line: 1

time-ms

with-meta

(with-meta obj m)

Returns an object of the same type and value as obj, with an object as its metadata.

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