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(ns ^{:next "Names and Places" :next-url "/labs/names-and-places"}
labs.intro
(:use [labrepl.util :only (code)]))
(defn overview []
[[:h3 "Overview"]
[:p "In this lab you will learn to
call functions from the Clojure Read-Eval-Print Loop (REPL), and a
set of tools that you can use from the REPL to explore Clojure. Note
that some of these tools are not available with a minimal install of
Clojure. Later in the course you will see how to include all of
these tools in your own projects."]
[:p "You need to be running the
labrepl to perform the steps in this lab."]])
(defn functions []
[[:h3 "Functions"]
[:ol
[:li "Find your labrepl window, which should have a prompt like " (code "user=> ")
"This prompt tells you that you are currently working in the user
namespace, which is a scratch namespace for experimenting. From the
prompt, you can call functions with forms like this:"
(code "(funcname arg1 arg2 ...)")
[:li "Go ahead and try \"hello world.\""
(code "(println \"hello world\")")]
[:li "Function names do not have to be words. Try some math functions:"
(code (+ 1 2)
(/ 22 7)
(/ 22.0 7)
(+ 1 2 3 4 5))]
[:li "You can define your own functions with " [:code "defn"] ".
Use the following form to define a function named triple that triples
its argument."
(code (defn triple
[arg]
(* 3 arg)))]
[:li "Try defining and calling a few other functions of your choosing."]]]])
(defn documentation []
[[:h3 "Documentation"]
[:ol
[:li "To learn about a function, you can examine its docstring. Print the
docstring for " [:code "println"] " using the form"
(code (doc println))]
[:li "If you are not sure of the name of a function, you can search for docs with "
[:code "find-doc"] ". This can sometimes return a huge amount of
information! Try " (code (find-doc "append"))]
[:li [:code "find-doc"] " can also handle regular expressions, which in Clojure
look like strings prepended by an octothorpe. Use a regular expression to
find all the " [:code "find-"] " functions." (code (find-doc #"find-\w+"))]
[:li "There is no documentation like the source code. Use " [:code "source"]
" to view the soure code of a function." (code (source println))]
[:li "Notice how the source for " [:code "println"] " includes a string before
the arguments. This is how you define docstrings. Try it with your own
functions: "
(code (defn triple
"Triples arg. Don't write redundant docstrings like this in real code."
[arg]
(* 3 arg)))
(code (doc triple))]]])
(defn java []
[[:h3 "Java"]
[:ol
[:li "Clojure provides direct, unproxied access to Java. To call a static
function use a form like " (code "(ClassName/function & args)")
"(The " [:code "& args"] " is shorthand for zero or more arguments.)
Try calling" (code (System/getProperty "java.home"))]
[:li "You can create Java instances with forms like " (code (new ClassName & args))
" or the terser, more idiomatic " (code (ClassName. & args)) " Try making
a date. " (code (java.util.Date.))]
[:li "Once you have an instance you probably will want to call methods on it.
For now, stuff your date into a global using " [:code "def"] ": "
(code (def now (java.util.Date.)))]
[:li "You can call instance methods like so:" (code (.getMonth now)
(.toGMTString now))]
[:li "If you can't remember all the date methods off the top of your
head, you can pass either a class or an instance to " [:code "javadoc"]
(code (javadoc now)
(javadoc java.util.Date))]]])
(defn bonus []
[[:h3 "Bonus"]
"What do you think the following forms will do?"
(code (doc doc))
(code (find-doc "find-doc"))
(code (source source))
(code (javadoc javadoc))
"Try them. Do you understand what you are seeing?"])
(defn instructions []
(concat (overview)
(functions)
(documentation)
(java)
(bonus)))
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