Clojure Inside Out Why is Clojure the most interesting new language on the horizon? Then Ford and Halloway take you much deeper into the language, while keeping the focus on practical application: Learn how to leverage macros to solve real problems Discover how Clojure helps you manage time the way garbage collection helps you manage space Understand why functional programming is so important Clojure represents a vision for building software that could only be implemented by building a new language. Stuart shows how interactive coding using the Clojure REPL creates a dynamic and fast feedback loop between intent and result.
After a few months of this sleepless schedule, my emotions took on a life of their own. As I watched the story of a formerly bald individual, I became overwhelmed with sincere joy. What an incredible product, giving hope to the hopeless! Some kind of potion, perhaps—a couple quaffs to unleash my inner Richard Simmons, but not for too long.
With macros, you can extend Clojure to suit your problem space, building up the language. Macros Are Essential Before you start writing macros, I want to help you put them in the proper context. In fact, macros allow Clojure to derive a lot of its built-in functionality from a tiny core of functions and special forms.
Take when, for example. However, when is actually a macro.
In this macro expansion, you can see that when is implemented in terms of if and do: Anatomy of a Macro Macro definitions look much like function definitions. They have a name, an optional document string, an argument list, and a body. The body will almost always return a list. This makes sense because macros are a way of transforming a data structure into a form Clojure can evaluate, and Clojure uses lists to represent function calls, special form calls, and macro calls.
You can use any function, macro, or special form within the macro body, and you call macros just like you would a function or special form. You can see this in the example.
Then the macro can use first, second, and last to rearrange the list so Clojure can evaluate it: You can also use argument destructuring in macro definitions, just like you can with functions: Here, infix-2 takes a sequential data structure as an argument and destructures by position so the first value is named operand1, the second value is named op, and the third value is named operand2 within the macro.
You can also create multiple-arity macros, and in fact the fundamental Boolean operations and and or are defined as macros. If a form returns logical false nil or falseand returns that value and doesn't evaluate any of the other expressions, otherwise it returns the value of the last expr.
Building Lists for Evaluation Macro writing is all about building a list for Clojure to evaluate, and it requires a kind of inversion to your normal way of thinking. Distinguishing Symbols and Values Say you want to create a macro that takes an expression and both prints and returns its value.
This differs from println in that println always returns nil. You want your macro to return lists that look like this: The reason this happens is that your macro body tries to get the value that the symbol let refers to, whereas what you actually want to do is return the let symbol itself.
There are other problems, too: This tells Clojure to turn off evaluation for whatever follows, in this case preventing Clojure from trying to resolve the symbols and instead just returning the symbols.
If we evaluate this plus symbol, it yields the plus function: If logical true, evaluates body in an implicit do. Indeed, you could write macros that way until the cows come home.Password requirements: 6 to 30 characters long; ASCII characters only (characters found on a standard US keyboard); must contain at least 4 different symbols;.
Profil użytkownika: aptitude. Zobacz moje wpisy na ashio-midori.com (strona 2). Writing Macros.
When I was 18, macros allow you to modify Clojure in ways that just aren’t possible with other languages. With macros, you can extend Clojure to suit your problem space, building up the language. once ingested, would temporarily give me the power and temperament of an ’80s fitness guru, freeing me from a prison of.
Clojure provides the get and get-in functions for returning values from a map and the Clojure: select-keys, select-values, and apply-values & apply-values to be helpful when writing.
With so many data formats out there, it's good to see some example code for reading and writing different formats. I'm talking JSON, EDN, and more. This course explores how to read and write data formats using Clojure.
edn Testing ashio-midori.com Leiningen Configuration Practice Clojure standard library (ashio-midori.com) Practice Clojure. Write lots of small and relatively simple examples in Clojure and experiment with the code in the REPL and try break things. Password requirements: 6 to 30 characters long; ASCII characters only (characters found on a standard US keyboard); must contain at least 4 different symbols;. We want to write code that is portable; it will run in Clojure and ClojureScript and produce identical (or, in some cases, similar) results. Sharing Portable Code We need a way to share portable code so that we only have to write it once.
I would like to write out an EDN data file from Clojure as tagged literals. Although the ashio-midori.com API contains read and read-string, there are no writers. I'm familiar with the issue reported here.