Terra - Programming language

Terra is an open source programming language created in 2012.

#230on PLDB

12Years Old

410Repos

Download source code:

git clone https://github.com/zdevito/terra

Terra is a low-level system programming language that is embedded in and meta-programmed by the Lua programming language:

Tags: programming language
Terra is developed on GitHub and has 2,692 stars
There are at least 410 Terra repos on GitHub
Terra is written in C++, Lua, Markdown, C, CMake, Bourne shell, YAML, JavaScript, HTML, CSS, Dockerfile, Make, Nix, Diff
The Google BigQuery Public Dataset GitHub snapshot shows 195 users using Terra in 206 repos on GitHub
Explore Terra snippets on Rosetta Code
GitHub supports syntax highlighting for Terra

Example from the web:

-- This top-level code is plain Lua code.
function printhello()
    -- This is a plain Lua function
    print("Hello, Lua!")
end
printhello()

-- Terra is backwards compatible with C, we'll use C's io library in our example.
C = terralib.includec("stdio.h")

-- The keyword 'terra' introduces a new Terra function.
terra hello(argc : int, argv : &rawstring)
    -- Here we call a C function from Terra
    C.printf("Hello, Terra!\n")
    return 0
end

-- You can call Terra functions directly from Lua, they are JIT compiled
-- using LLVM to create machine code
hello(0,nil)

-- Terra functions are first-class values in Lua, and can be introspected
-- and meta-programmed using it
hello:disas()
--[[ output:
    assembly for function at address 0x60e6010
    0x60e6010(+0):    push  rax
    0x60e6011(+1):    movabs  rdi, 102129664
    0x60e601b(+11):   movabs  rax, 140735712154681
    0x60e6025(+21):   call  rax
    0x60e6027(+23):   xor eax, eax
    0x60e6029(+25):   pop rdx
    0x60e602a(+26):   ret
]]

-- You can save Terra code as executables, object files, or shared libraries
-- and link them into existing programs
terralib.saveobj("helloterra",{ main = hello })

Example from hello-world:

print("Hello World")

Example from Linguist:

C = terralib.includecstring [[
	#include <stdio.h>
	#include <stdlib.h>
]]
local arraytypes = {}
function Array(T)
	local struct ArrayImpl {
		data : &T;
		N : int;
	}
	function ArrayImpl.metamethods.__typename(self)
	    return "Array("..tostring(T)..")"
	end
	arraytypes[ArrayImpl] = true
	terra ArrayImpl:init(N : int)
		self.data = [&T](C.malloc(N*sizeof(T)))
		self.N = N
	end
	terra ArrayImpl:free()
		C.free(self.data)
	end
	ArrayImpl.metamethods.__apply = macro(function(self,idx)
		return `self.data[idx]
	end)
	ArrayImpl.metamethods.__methodmissing = macro(function(methodname,selfexp,...)
		local args = terralib.newlist {...}
		local i = symbol(int)
		local promotedargs = args:map(function(a)
			if arraytypes[a:gettype()] then
				return `a(i)
			else
				return a
			end
		end)
		return quote
			var self = selfexp
			var r : ArrayImpl
			r:init(self.N)
			for [i] = 0,r.N do
				r.data[i] = self.data[i]:[methodname](promotedargs)
			end
		in
			r
		end
	end)
	return ArrayImpl
end

struct Complex {
	real : float;
	imag : float;
}

terra Complex:add(c : Complex)
	return Complex { self.real + c.real, self.imag + c.imag }
end

ComplexArray = Array(Complex)
N = 10
terra testit()
	var ca : ComplexArray
	ca:init(N)
	for i = 0,N do
		ca(i) = Complex { i, i + 1 }
	end
	var ra = ca:add(ca)
	return ra
end
local r = testit()
assert(r.N == N)
for i = 0,N-1 do
	assert(r.data[i].real == 2*i)
	assert(r.data[i].imag == 2*(i+1))
end
assert(tostring(Array(int)) == "Array(int32)")

Language features

Feature	Supported	Example	Token
Strings	✓	"Hello world"	"
Print() Debugging	✓		print
Comments	✓	-- A comment
Line Comments	✓	-- A comment	--
Semantic Indentation	X