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+---
+name: Red
+category: language
+language: Red
+filename: learnred.red
+contributors:
+    - ["Arnold van Hofwegen", "https://github.com/iArnold"]
+---
+
+
+Red was created out of the need to get work done, and the tool the author wanted to use, the language of REBOL, had a couple of drawbacks.
+It was not Open Sourced at that time and it is an interpreted language, what means that it is on average slow compared to a compiled language.
+
+Red, together with its C-level dialect Red/System, provides a language that covers the entire programming space you ever need to program something in.
+Red is a language heavily based on the language of REBOL. Where Red itself reproduces the flexibility of the REBOL language, the underlying language Red will be built upon,
+Red/System, covers the more basic needs of programming like C can, being closer to the metal.
+
+Red will be the world's first Full Stack Programming Language. This means that it will be an effective tool to do (almost) any programming task on every level
+from the metal to the meta without the aid of other stack tools.
+Furthermore Red will be able to cross-compile Red source code without using any GCC like toolchain
+from any platform to any other platform. And it will do this all from a binary executable that is supposed to stay under 1 MB.
+
+Ready to learn your first Red?
+
+```
+All text before the header will be treated as comment, as long as you avoid using the
+word "red" starting with a capital "R" in this pre-header text. This is a temporary
+shortcoming of the used lexer but most of the time you start your script or program
+with the header itself.
+The header of a red script is the capitalized word "red" followed by a
+whitespace character followed by a block of square brackets [].
+The block of brackets can be filled with useful information about this script or
+program: the author's name, the filename, the version, the license, a summary of
+what the program does or any other files it needs.
+The red/System header is just like the red header, only saying "red/System" and
+not "red".
+
+Red []
+
+;this is a commented line
+
+print "Hello Red World"    ; this is another comment
+
+comment {
+    This is a multiline comment.
+    You just saw the Red version of the "Hello World" program.
+}
+
+; Your program's entry point is the first executable code that is found
+; no need to restrict this to a 'main' function.
+
+; Valid variable names start with a letter and can contain numbers,
+; variables containing only capital A thru F and numbers and ending with 'h' are
+; forbidden, because that is how hexadecimal numbers are expressed in Red and
+; Red/System.
+
+; assign a value to a variable using a colon ":"
+my-name: "Red"
+reason-for-using-the-colon: {Assigning values using the colon makes
+ the equality sign "=" exclusively usable for comparisons purposes,
+ exactly what "=" was intended for in the first place!
+ Remember this y = x + 1 and x = 1 => y = 2 stuff from school?
+}
+is-this-name-valid?: true
+
+; print output using print, or prin for printing without a newline or linefeed at the
+; end of the printed text.
+
+prin " My name is " print my-name
+My name is Red
+
+print ["My name is " my-name lf]
+My name is Red
+
+; In case you haven't already noticed: statements do NOT end with a semicolon ;-)
+
+;
+; Datatypes
+;
+; If you know Rebol, you probably have noticed it has lots of datatypes. Red
+; does not have yet all those types, but as Red want to be close to Rebol it
+; will have a lot of datatypes.
+; You can recognize types by the exclamation sign at the end. But beware
+; names ending with an exclamation sign are allowed.
+; Some of the available types are integer! string! block!
+
+; Declaring variables before using them?
+; Red knows by itself what variable is best to use for the data you want to use it
+; for.
+; A variable declaration is not always necessary.
+; It is considered good coding practise to declare your variables,
+; but it is not forced upon you by Red.
+; You can declare a variable and specify its type. a variable's type determines its
+; size in bytes.
+
+; Variables of integer! type are usually 4 bytes or 32 bits
+my-integer: 0
+; Red's integers are signed. No support for unsigned atm but that will come.
+
+; To find out the type of variable use type?
+type? my-integer
+integer!
+
+; A variable can be initialized using another variable that gets initialized
+; at the same time.
+i2: 1 + i1: 1
+
+; Arithmetic is straightforward
+i1 + i2 ; result 3
+i2 - i1 ; result 1
+i2 * i1 ; result 2
+i1 / i2 ; result 0 (0.5, but truncated towards 0)
+
+; Comparison operators are probably familiar, and unlike in other languages you
+; only need a single '=' sign for comparison.
+; There is a boolean like type in Red. It has values true and false, but also the
+; values on/off or yes/no can be used
+
+3 = 2 ; result false
+3 != 2 ; result true
+3 > 2 ; result true
+3 < 2 ; result false
+2 <= 2 ; result true
+2 >= 2 ; result true
+
+;
+; Control Structures
+;
+; if
+; Evaluate a block of code if a given condition is true. IF does not return any value,
+; so cannot be used in an expression.
+if a < 0 [print "a is negative"]
+
+; either
+; Evaluate a block of code if a given condition is true, else evaluate an alternative
+; block of code. If the last expressions in both blocks have the same type, EITHER can
+; be used inside an expression.
+either a < 0 [
+   either a = 0 [
+       msg: "zero"
+   ][
+       msg: "negative"
+   ]
+][
+   msg: "positive"
+]
+
+print ["a is " msg lf]
+
+; There is an alternative way to write this
+; (Which is allowed because all code paths return a value of the same type):
+
+msg: either a < 0 [
+   either a = 0 [
+       "zero"
+   ][
+       "negative"
+   ]
+ ][
+   "positive"
+]
+print ["a is " msg lf]
+
+; until
+; Loop over a block of code until the condition at end of block, is met.
+; UNTIL does not return any value, so it cannot be used in an expression.
+c: 5
+until [
+   prin "o"
+   c: c - 1
+   c = 0    ; the condition to end the until loop
+]
+;   will output:
+ooooo
+; Note that the loop will always be evaluated at least once, even if the condition is
+; not met from the beginning.
+
+; while
+; While a given condition is met, evaluate a block of code.
+; WHILE does not return any value, so it cannot be used in an expression.
+c: 5
+while [c > 0][
+   prin "o"
+   c: c - 1
+]
+; will output:
+ooooo
+
+;
+; Functions
+;
+; function example
+twice: function [a [integer!] /one return: [integer!]][
+        c: 2
+        a: a * c
+        either one [a + 1][a]
+]
+b: 3
+print twice b   ; will output 6.
+
+; Import external files with #include and filenames start with a % sign
+#include %includefile.red
+; Now the functions in the included file can be used too.
+
+```
+
+## Further Reading
+
+The main source for information about Red is the [Red language homepage](http://www.red-lang.org).
+
+The source can be found on [github](https://github.com/red/red).
+
+The Red/System language specification can be found [here](http://static.red-lang.org/red-system-specs-light.html).
+
+To learn more about Rebol and Red join the [chat on Gitter](https://gitter.im/red/red). And if that is not working for you drop a mail to us on the [Red mailing list](mailto: red-langNO_SPAM@googlegroups.com) (remove NO_SPAM).
+
+Browse or ask questions on [Stack Overflow](stackoverflow.com/questions/tagged/red).
+
+Maybe you want to try Red right away? That is possible on the [try Rebol and Red site](http://tryrebol.esperconsultancy.nl).
+
+You can also learn Red by learning some [Rebol](http://www.rebol.com/docs.html).