This new release is bringing a lot of important bug fixes and some new features for Red/System. The new PRINT function might break some existing scripts, but should be easily fixable.
PRINT function examples:
print 123 123 print "hello" hello print [123 "hello"] 123hello print [123 tab "hello" lf "world" lf] 123 hello world a: 1 < 2 b: "hello" print [a tab b/2] true e
As you can see, no vacation this summer for Red project!
This new milestone brings (finally) functions to Red along with other new features and fixes. Let’s first have a quick overview of 0.3.1 release content:
function!, paren!, path!, lit-path!, get-path!, set-path!
find, select, copy, reflect,
mold, formand comparison operators to all new and existing datatypes
They are declared using a similar syntax to REBOL, with some extensions. The specification block looks like this:
[arg1 [type1] arg2 [type2]...return: [type] /local var1 [type-v1]...]
All type specifiers are optional, adding them will not only allow the compiler to make additional type checkings but also generate faster code in some cases (once the optimizations added to the Red compiler).
Note: argument and return value type checking have not been implemented yet, they need typeset! and error! datatypes to be implemented first.
Functions can be built using several constructors:
function: automatically collects local variables, like
twice: function [a [integer!] /one return: [integer!]][ c: 2 a: a * c either one [a + 1][a] ]
func: low-level function constructor, everything needs to be manually specified.
twice: func [a [integer!] /one return: [integer!] /local c][ c: 2 a: a * c either one [a + 1][a] ]
has: no argument, just lists local words.
globals: [1 2 3 _] foobar: has [list][ if list: find globals '_ [clear list] ]
does: no argument, no local words.
quit: does [ print "Goodbye cruel world!" halt ]
Early exit points are also there in form of
foobar: func [a [integer!] b [integer! none!]][ if none' b [return none] if b = 0 [ print "Error: division by zero" exit ] a / b ]
Refinements are also fully supported, when not used, their value is set to
false (while in REBOL it is set to
Still some features are not yet implemented:
Currently functions are using a local context on stack, so their life-time is very short. For indefinite extent support, a closure! type will be added in the next months.
Path datatypes were added (
path!, lit-path!, get-path!, set-path!) to the runtime library and compiler, allowing the use of path notation as syntactic sugar for series access. Getting and setting values using path notation are supported.
Some usage examples:
list: [a 5 b [c 8] d #"e" name: "John"] probe list/2 ;-- outputs 5 probe list/7 ;-- outputs name: probe list/a ;-- outputs 5 probe list/4/2 ;-- outputs 8 probe list/b/c ;-- outputs 8 probe list/name ;-- outputs "John" list/b/c: 0 probe list/b/c ;-- outputs 0 index: 3 probe list/:index ;-- outputs b list/:index: 'z probe list/:index ;-- outputs z
Note: notice how words lookups in blocks can work with any word datatypes.
Paren! datatype and expressions in parentheses compilation support has been added too. They are mainly useful with infix operators in order to force a given execution priority. Example:
print (1 + 2) * (3 + 4) ;-- outputs 21
function, func, does, has, exit, return
probe, first, second, third, fourth, fifth, last, spec-of, body-ofand all <datatype>’ type testing functions.
Existing native or action functions were extended with refinements (like
form). See the boot.red script for more details.
The Quick-Test framework from Peter WA Wood was ported to Red and now powers all the current 1800+ unit tests written in Red itself, mostly added by Peter.
About 32 issues/bugs in both Red and Red/System were fixed in this new release.
Last but not least, Rudolf updated his Red/System formal description document [PDF, 162KB] to include the additional features like namespaces. Many thanks to him for his remarkable work and support to Red project!
Objects support is next priority along with new natives like
case. Typesets and error handling will probably be added very soon too. Once that part done, the next focus will be to add I/O support!
Many thanks to all the people that have made significant donations in last months to Red project, allowing me to continue to work full time on it! It is really making a big difference, as shown by Red increased progress speed since this summer. Thanks again!
Here is a quick update on Red/System progress.
Draft has gone through several revisions. Several decisions mainly regarding pointers handling have been taken with simplification and disambiguation as main goals:
A couple of things to keep in mind about Red/System design:
Several items from the todo-list have been implemented in the last week, the most notable ones being:
Among other changes:
An interesting side note on how implementation can influence back the design:
During the implementation of Quick Test framework, Peter, while writing an integer to string conversion function, came up with a code pattern that is common in REBOL, but wasn’t planned for Red/System: declaring private functions inside a function to hide them from global context. The pattern looked like this:
prin-int: func [...][ ... prin-digit: func [...][...] ... prin-digit ... ... ]
I was surprised when I tested the code he sent me, as I never did anything in the implementation to support such case explicitly. It was working because of a side-effect caused by the way functions are compiled in Red/System: the functions bodies are all gathered and compiled at the end of the global context code, regardless of where they are defined. The side-effect making the inner “prin-digit” function private is caused by a global function variable being declared inside a local scope, but without being part of the function specification block. So, once the outer function compiled, the “prin-digit” symbol is lost, making the function unreachable from global context and forever hidden.
I was thinking about adding a way for users to create private contexts much later in the future (relying on Red/System source header), but we have the opportunity to have an equivalent feature, right now and without adding anything to the code! So, I am giving it some time to see if the side-effect can be safely made permanent to keep that feature, and in the meantime, added it to the Possible Evolutions part of the specifications.
In the next days, I will work on:
In my next blog article, I will give an overview of Red/System compiler internals as requested by some followers.