npm i oppo
This package doesn't really work and was just an educational exercise. It shouldn't really be on npm, but since it seems to be getting downloaded I'll leave it up. Bottom line, if you want this to work for you, you should probably just fork the project.


If javascript is lisp in c's clothing, then oppo is lisp in lisp's clothing, with c's pajamas.

by Paul Harper

0.1.3 (see all)TypeScript:Not Found
npm i oppo

Note to anyone who may care: I haven't used or substantially updated this project in a long time and do not plan on putting any further effort into it. The npm package has been deprecated to reflect this. If you want this to work for you, feel free to fork it.


Oppo is a sweet little lisp for javascript. This is experimental, and therefore any suggestions are welcome.


To install, run the following in your terminal. Make sure you have node.js and npm installed first.

npm install -g oppo@0.1.2 # The repl doesn't work properly in 0.1.3

Now you have access to the oppo command. To enter the repl:



oppo -r

To compile a file:

oppo -c /path/to/file.oppo

You can also specify an output file:

oppo -o /path/to/file.js -c /path/to/file.oppo

In the previous command, if you have uglify-js2 installed globally, it will prettify the resulting javascript. You could pass the -C switch to have it compress your code instead.

To run a file:

oppo /path/to/file.oppo

Language Overview

The basics

Since oppo is a lisp, it takes on the basic semantics of a lisp. Oppo isn't dissimilar to scheme or clojure, so if you want to get a feel for the basic semantics of lisp, there's plenty of code out there to look at.

Here are some specifics about the way oppo is parsed:


  • Integer: 2, -5
  • Float: -2.5, .34
  • Scientific notation: 10e-2.5
  • Explicit base: 2#001101, 8#1427, 16#fff


"whatever". If you need to escape a double-quote, you can use \".


Oppo accepts most characters as valid symbols. Symbols can't start with a number or any of the following sequences: #, ", ', \``, ,, ,@, .`. Symbols can't contain any kind of whitespace. Anything else on the US keyboard is fair game.


Lists are code. Oppo code is primarily a tree of lists. All lists are executable. The basic way to make a list is to put space-separated items in parenthesis:

(puts "I" "am" "a" "list")

Since lists are executable, this will call the puts macro, which will log the rest of the items in the list to the console. If you don't want your list to be executed you can quote it or use a literal array:

'(1 2 3) ;; Won't try to call this as a function
#[1 2 3] ;; Same result


Oppo only thinks of objects as data and never tries to execute an object. Objects are made like this:

#{'a 1 'b 2}

You can do some interesting things with oppo objects that you can't do in javascript (at least not as easily). For example, keys can be variables in the same way their values can:

(def key 'asdf)
(def value 5)
#{key value} ;; -> #{asdf 5}


Oppo uses the lambda macro to generate functions. There is also a reader macro #(...) which acts as a shorthand for the lambda macro. You can also define a function with the def macro:

(lambda (a b) (+ a b))

#(+ #1 #2) ;; #1 and #2 access the 0th and 1st arguments respectively

(def (add-a-b a b)
  (+ a b))

Language Documentation

Following is a list of macros, functions and variables available to the oppo programmer. Entries take the format of <module>::<item-name>. The core module is automatically available, so you don't have to use the module prefix in that case. As an example, you can call core::str by simply invoking str (unless you have replaced str in your current module or in an active local scope).

core module

  • macro core::defmacro: (defmacro optional-metadata (macro-name ...args) ...body) Defines a macro.


    (defmacro (log ...x)
      `(.log console ,@x))
  • macro core::def: (def optional-metadata name value) | (def optional-metadata (fn-name ...args) ...body) Defines a variable on the current module.


    ;; Define module variable
    (def one 1)
    ;; Define function
    (def (identity x) x)
  • macro core::set!: (set! name value) Resets the value of a variable.


    (def n 1)
    (set! n (+ n 1))
  • macro core::lambda: (lambda (...args) ...body) Creates a function. You can also use the #(...) reader macro for this. Arguments that aren't named can still be accessed from the arguments object. A reader macro is provided for this as well, #1 where the 1 can be any number greater than 0. #1 will access the 0th argument, #2 the first argument and so on.


    (map (lambda (a)
           (+ a 1)) #[1 2 3 4 5]) ;; -> #[2 3 4 5 6]
    (map #(+ #1 1) #[1 2 3 4 5]) ;; -> #[2 3 4 5 6]
  • macro core::call: (call callable-item ...args) This is used internally for all function/macro calling. This is not generally the way you will need to call things.


    (call puts 1 2 3)
    ;; The normal way to call things is without `call`.
    ;; Running it this way will do the same thing as the line above.
    (puts 1 2 3)
  • macro core::object-get-value: (object-get-value prop base) Gets the value with the corresponding prop in a collection. You shouldn't often need to invoke this directly. See example below.


    (object-get-value 'alert window)
    ;; Here's a better way to do this:
    ('alert window)
    ;; or
    ("alert" window)
  • macro core::.: (. fname base ...args) Gets a callable value from base and immediately calls it with args. Because of a handy reader macro, there doesn't need to be a space separating the . from the fname.


    (.alert window 5)
    (."static" express)
  • macro core::quote: (quote x) Quotes x. Instead of using the explicit call, most of the time you will want to use the reader macro '.


    (quote x) ;; -> x
    'x ;; -> x
  • macro core::quasiquote: (quasiquote x) Quasiquotes x. You can also use the reader macro ```.


    (def a 5)
    `(1 2 3 4 a ,a) ;; -> '(1 2 3 4 a 5)
  • macro core::unquote: (unquote x) Unquotes x. You can also use the reader macro ,.


    (def a 5)
    `(1 2 3 4 a ,a) ;; -> '(1 2 3 4 a 5)
  • macro core::unquote-splicing: (unquote-splicing x) Unquotes each item in x in sequence into another structure. You can also use the reader macro ,@.


    (def a #[1 2 3 4 5])
    `(0 ,@a 6) ;; -> #[0 1 2 3 4 5 6]
  • macro core::let: (let (...bindings) ...body) Introduces a local scope. bindings are the local variables. It will run each item in body in this new local scope and return the result of the last item.


    (let [a 1
          b 2
          c 3]
       (+ a b c)) ;; -> 6
  • macro core::if: (if condition run-if-true optional-run-if-false) if expression.


    (if (nil? x)
  • macro core::for: (for [defs ls] ...body) The for expression is very similar to map, but can be much faster.


    ;; `n` represents an item in the array.
    (for [n #[1 2 3 4 5]] (* n 2)) ;; -> #[2 4 6 8 10]
    ;; `n` represents an item in the array and `i` represents the index.
    (for [(n i) #[1 2 3 4 5]] (+ n i)) ;; -> #[1 3 5 7 9]
  • macro core::do: (do ...body) do will run each item in body and give you the result of the last statement.


    (if (< n 5)
        (puts n)
        (set! n (+ n 1))))
  • macro core::include: (include ...module-names) This will find and compile each module. If the module has already been compiled, then it is already available and will not attempt to compile it again.

    Modules are simple directory paths that are resolved in the same base directory as the main file. Generally, you should only send one single file to the oppo compiler, and this file will include all the modules it needs, and those modules will include the modules they need, and so forth. In this way, the compiler will get all the source files used and compile them all into a single javascript file.


    (include routes/main routes/users)
    (.get app "/" routes/main::home)
    (.get app "/user/:id" routes/users::show)
  • macro core::apply: (apply fn args) This is the same as using the javascript .apply function, except you can't specify scope.

  • macro core::require: (require module-name) | (require varname module) Makes using the node.js require function (or any implementation similar enough) simpler to use.


    (require express) ;; var express = require('express');
    (require routes "./routes") ;; var routes = require('./routes');
  • macro core::new: (new Class ...args) Allows you to instantiate a class.

  • macro core::puts: (puts ...args) Logs output to the console.

  • macro core::puts-warning: (puts-warning ...args) Logs warning message to the console.

  • macro core::puts-error: (puts-error ..args) Logs error message to the console.

  • macro core::cond: (cond cond1 body1 cond2 body2 cond-n body-n) Evaluates each condition until it finds one that is true. When it finds a true condition, it executes the corresponding body.


    (def n 3)
      (eq n 1) (puts "one")
      (eq n 2) (puts "two")
      (eq n 3) (puts "three")
      'else (puts "idk")) ;; will print "three" to the console.
  • macro core::use-from: (use-from module ...items) Extracts items from module and defines a copy locally.


    (use-from js eval
                 typeof) ;; Now the macros eval and typeof are
    available in the current scope.
  • macro core::use: (use module1 defs1 module2 defs2 module-n defs-n) With each module and defs pair, it calls use-from.


    (use module-a [a b c]
         module-b [d e f])
  • macro/function core::symbol: (make-symbol x) Generates a symbol from x.


    (symbol 'asdf)
    (symbol "asdf")
  • Basic operations These are all of type macro/function, and are all in the module core. They all correspond with the same operator in javascript unless otherwise noted.


    • +
    • -
    • *
    • /


    • not (javascript !)
    • or (javascript ||)
    • and (javascript &&)


    • <
    • >
    • <=
    • >=
    • eq (javascript ===)
    • not-eq (javascript !==)
    • eq~ (javascript ==)
    • not-eq~ (javascript !=)
  • Type checking All the following are of type function/macro and check to see that their argument is equal to the type the name describes. (For example, (number? x) returns true when x is a number). All are in the core module.

    • number?
    • string?
    • array?
    • arguments? (returns true when its argument is a function's arguments object.)
    • nil? (returns true when its argument is either null or undefined.)
    • function?
    • regex?
    • date?
  • function core::typeof: (typeof x) This is the toType function by Angus Croll found here.

  • function core::eval: (eval to-eval) This invokes oppo's compiler on to-eval, evals the compiled code using the javascript eval function and returns the computed result.


    (eval '(+ 1 1)) ;; -> 2
  • function core::empty?: (empty? coll) Checks to see if a collection is empty. Accepts argument of any type. Empty arrays, objects and strings will return true. Additionally, #nil and 0 will also return true. Anything else will return false.

  • function core::contains?: (contains? coll value optional-deep-eq) Checks to see if the collection contains the value. optional-deep-eq is #true by default. If it is set to #false, it will use the === operator for comparison rather than the oppo = function.

  • function core::contains-key?: (contains-key? coll, key) Checks to see if the collection contains the given key. Works for arrays, the arguments object, strings and objects. If you pass something else for coll, the result will be #false.

  • function core::list: (list ...args) Makes a list out of the arguments. You can call this function directly, or you can use the #[...] reader macro.


    (= (list 1 2 3) #[1 2 3]) ;; -> #true
  • function core::->list: (->list object) Turns any object with a length property into a list.

  • function core::map: (map fn list) Invokes fn with each item in list and gathers the results of those calls into an array, which is returned. Similar to for.


    (def ls #[1 2 3 4 5])
    (map #(* #1 2) ls) ;; -> #[2 4 6 8 10]
  • function core::reduce: (reduce fn list) Invokes fn with the first two items in list, gets the result, and then continues through the rest of the list calling fn with the previous result and the next item in the list until the list is exhausted. Returns the final result.


    (def ls #[1 2 3 4 5])
    (reduce * ls) ;; -> 120
  • function core::reduce-right: (reduce-right fn list) Same as core::reduce, but operates on the list in reverse.

  • function core::filter: (filter fn list) Invokes fn on each item in the list and returns a new list of all the items for which fn returned a truthy value.


    (def (is-odd? n)
      (> (mod n 2) 0))
    (def ls #[0 1 2 3 4 5 6])
    (filter is-odd? ls) ;; -> #[1 3 5]
  • function core::concat: (concat ls1 ls2 ls-n) This works on lists and strings, but if you are working on lists then each ls must be a list and if you are working on strings then each ls must be a string. It uses the native concat method for lists and strings respectively.

  • function core::first: (first ls) Returns the first item in an ordered collection.

  • function core::second: (second ls) Returns the second item in an ordered collection.

  • function core::third: (third ls) Returns the third item in an ordered collection.

  • function core::last: (last ls) Returns the last item in an ordered collection.

  • function core::slice: (slice ls start optional-end) Returns a list of all the items between start and either optional-end or the end of the list.

  • function core::head: (head ls) Returns a new list of all the items in ls except the last one.

  • function core::tail: (tail ls) Returns a new list of all the items in ls except the first one.

  • function core::nth: (nth ls n) Returns the nth item of ls. Operates on ls as if it were 1-indexed.


    (def ls #[1 2 3])
    (nth ls 1) ;; -> 1
  • function core::object: (object key1 value1 key2 value2 key-n value-n) Creates an object. You can also use the reader macro #{...}


    (object 'a 1 'b 2 'c 3 'd 4 'e 5) ;; -> #{a 1
                                              b 2
                                              c 3
                                              d 4
                                              e 5}
  • function core::->object: (->object x) Converts x into an Object.

  • function core::merge: (merge ...objects) Creates a new object with the combined properties of each object passed in. If there are conflicts, objects passed in later will have priority.


    (def o1 #{'a 1 'b 2 'c 3})
    (def o2 #{'a #nil 'd 4})
    (merge o1 o2) ;; -> #{a #nil
                          b 2
                          c 3
                          d 4}
  • function core::keys: (keys obj) Returns all direct keys of any object. This will not return keys on the prototype of the object.

  • function core::str: (str ...strings) Concatenates all strings into a single string. Arguments do not have to explicitly be a string. If they are not a string, they will be converted into a string for the final result.

  • function core::->string: (->string x) Converts x into a string.

  • function core::->number: (->number x) Converts x into a number.

  • function core::->boolean: (->boolean x) Converts x into a boolean.

  • function core::=: (= ...items) Checks to see if all items are equal to each other. In the case of objects, = will check to see if the objects are similar enough to be considered equal.

  • function core::not=: (not= ...items) The inverse of core::=.

  • function core::list?: (list? x) Checks if x is a list (it is either an array or an arguments object).

  • function core::object?: (object? x) Checks if x is any kind of object.

  • function core::isNaN?: (isNaN? x) Checks if x is the isNaN primitive.

  • object core::global This refers to global when it is available and window otherwise.

js module

  • macro js::eval: (js::eval to-eval) If you pass in a string, js::eval will dump that string as-is into the compiler output. If you pass in anything else, it will be compiled normally and then passed to the javascript eval function.


    (def obj #{'a 1 'b 2})
    (if (js::eval "'a' in obj")
      (do-something obj))
  • macro js::typeof: (js::typeof x) This is the same as the javascript operator typeof.


    (typeof 5) ;; -> "number""
    (typeof #nil) ;; -> "object"



GitHub Stars



8yrs ago








10yrs ago
No alternatives found
No tutorials found
Add a tutorial