Carp borrows its looks from Clojure but the runtime semantics are much closer to those of ML or Rust.
Types are inferred but can be annoted for readability using the the keyword (see below).
Memory management is handled by static analysis, a value is owned by the function where it was created.
When a value is returned or passed to another function the initial function will give up ownership of it
and any subsequent use will lead to a compiler error. To temporarily lend a value to another function
(for example to print it) a reference must be created, using the ref special form (or the & reader macro).
To learn more about the details of memory management, check out Memory.md
;; Comments begin with a semicolon and continue until the end of the line.100 ;; Int
1500l ;; Long
3.14f ;; Float
10.0 ;; Double
true ;; Bool
"hello" ;; &String
\#"hello" ;; &Pattern
\e ;; Char
[1 2 3] ;; (Array Int)
{1 1.0 2 2.0} ;; (Map Int Double)t ;; Type variables begin with a lowercase letter
Int
Long
Float
Double
Bool
String
Pattern
Char
(Array t)
(Map <key-type> <value-type>)
(Fn [<arg-type1> <arg-type2> ...] <return-type>) ;; Function typeRight now the following data types are only available for manipulation in non-compiled code.
(1 2 3) ; list
foo ; symbol(defn function-name [<arg1> <arg2> ...] <body>) ;; Define a function (will be compiled, can't be called at the REPL)
(definterface interface-name (Fn [<t1> <t2>] <return>)) ;; Define a generic function that can have multiple implementations
(def variable-name value) ;; Define a global variable (only handles primitive constants for the moment)
(defmacro <name> [<arg1> <arg2> ...] <macro-body>) ;; Define a macro, its argument will not be evaluated when called
(defndynamic <name> [<arg1> <arg2> ...] <function-body>) ;; A function that can only be used at the REPL or during compilation
(defmodule <name> <definition1> <definition2> ...) ;; The main way to organize your program into smaller partsThe following forms can be used in Carp source code and will be compiled to C after type checking and other static analysis. The first three of them are also available in dynamic functions.
(fn [<arg1> <arg2> ...] <body>) ;; Create a lambda function (a.k.a. closure)
(let [<var1> <expr1> <var2> <expr2> ...] <body>) ;; Create local bindings
(do <expr1> <expr2> ... <return-expression>) ;; Perform side-effecting functions, then return a value
(if <expression> <true-branch> <false-branch>) ;; Branching
(while <expression> <body>) ;; Loop until expression is false
(ref <expression>) ;; Borrow an owned value
(address <expression>) ;; Takes the memory address of a value, returns a C-style pointer
(set! <variable> <expression>) ;; Mutate a variable
(the <type> <expression>) ;; Explicitly declare the type of an expressionHere's an example of how to use the the form to make an identity function that only accepts Integers:
(defn f [x]
(the Int x))&x ;; same as (ref x)
@x ;; same as (copy x)When using a statically typed language like Carp it can sometimes be hard to know what value should be used at a specific point in your program. In such cases the concept of 'holes' can be useful. Just add a hole in your source code and reload (":r") to let the Carp compiler figure out what type goes there.
(StringCopy.append ?w00t @"!") ;; Will generate a type error telling you that the type of '?w00t' is String(quote <expression>) ;; Avoid further evaluation of the expression
(and) (or) (not) ;; Logical operatorsThese can only be used at the REPL and during macro evaluation. Here's a subset with some of the most commonly used ones:
(car <collection>) ;; Return the first element of a list or array
(cdr <collection>) ;; Return all but the first element of a list or array
(cons <expr> <list>) ;; Add the value of <expr> as the first element the <list>
(cons-last <expr> <list>) ;; Add the value of <expr> as the last element the <list>
(list <expr1> <expr2> ...) ;; Create a list from a series of evaluated expressions
(array <expr1> <expr2> ...) ;; Create an array from a series of evaluated expressionsTo see all functions available in the Dynamic module, enter (info Dynamic) at the REPL.
Functions and variables can be stored in modules which are named and can be nested. To use a symbol inside a module
you need to qualify it with the module name, like this: Float.cos.
Using a module makes it possible to access its members without qualifying them:
(use Float)
(defn f []
(cos 3.2f))If there are several used modules that contain symbols with the same name, the type inferer will try to figure
out which one of the symbols you really mean (based on the types in your code). If it can't, it will display an error.
For example, both the module String and Array contain a function named 'length'. In the following code it's
possible to see that it's the array version that is needed, and that one will be called:
(use String)
(use Array)
(defn f []
(length [1 2 3 4 5]))In the following example it's not possible to figure out which type is intended:
(use String)
(use Array)
(defn f [x]
(length x))Specifying the type solves this error:
(use String)
(use Array)
(defn f [x]
(String.length x))(deftype Vector2 [x Int, y Int])
(let [my-pos (Vector2.init 10 20)]
...)
;; A 'lens' is automatically generated for each member:
(Vector2.x my-pos) ;; => 10
(Vector2.set-x my-pos 30) ;; => (Vector2 30 20)
(Vector2.update-x my-pos inc) ;; => (Vector2 11 20)(system-include "math.h") ;; compiles to #include <math.h>
(local-include "math.h") ;; compiles to #include "math.h"
(register blah (Fn [Int Int] String)) ;; Will register the function 'blah' that takes two Int:s and returns a String
(register pi Double) ;; Will register the global variable 'pi' of type Double
(register blah (Fn [Int Int] String) "exit") ;; Will register the function 'blah' but use the name 'exit' in the emitted C code.
(register-type Apple) ;; Register an opaque C type
(register-type Banana [price Double, size Int]) ;; Register an external C-structs, this will generate getters, setters and updaters.Patterns are similar to, but not the same as, Regular Expressions. They were derived from Lua, and are useful whenever you want to find something within or extract something from strings.
They are simpler than Regular Expressions, as they do not provide alternation. Nonetheless, they are often very useful and, because they are simpler, also faster and more predictable.
Here is a little overview of the API:
; you can initialize a pattern with a literal or create one from a string
#"[a-z]"
(Pattern.init "[a-z]")
; you can also get a string back from it
(str #"[a-z]")
(prn #"[a-z]")
; you can find things in strings by index
(Pattern.find #"[a-z]" "1234a") ; => 4
(Pattern.find #"[a-z]" "1234") ; => -1
; also multiple things at once!
(Pattern.find-all #"[a-z]" "1234a b") ; => [4 6]
; matches? checks whether a string matches a pattern
(Pattern.matches? #"(\d+) (\d+)" " 12 13") ; => true
; match returns all match groups of the first match
(Pattern.match #"(\d+) (\d+)" " 12 13") ; => ["12" "13"]
; match-str returns the whole string of the first match
(Pattern.match #"(\d+) (\d+)" " 12 13") ; => "12 13"
; global-match gets all match groups of all matches
(Pattern.global-match #"(\d+) (\d+)" " 12 13 14 15") ; => [["12" "13"] ["14" "15"]]
; substitute helps you replace patterns in a string n times
(Pattern.substitute #"sub-me" "sub-me sub-me sub-me" "replaced" 1) ; => "replaced sub-me sub-me"
; if you want to replace every occurrence, use -1
(Pattern.substitute #"sub-me" "sub-me sub-me sub-me" "replaced" -1) ; => "replaced replaced replaced"