OpenEuphoria

1. Nested constants

• Posted by petelomax Jun 22, 2020
• 945 views

Managed to shoehorn a little featurette in yesterday, took less than an hour.

Instead of

 
                constant WSAEINTR   = 10004, 
                         WSAEACCES  = 10013 
                constant {ERROR_NO, ERROR_NAME, ERROR_SHORT} = columnize( 
                    {{WSAEINTR,         "WSAEINTR",  "Interrupted function call."}, 
                     {WSAEACCES,        "WSAEACCES", "Permission denied."}} 
 

(which gets more and more error prone and tedious as the tables grow in size) you can now define them all together like this:

 
                constant {ERROR_NO, ERROR_NAME, ERROR_SHORT} = columnize( 
                    {{WSAEINTR :=10004, "WSAEINTR",  "Interrupted function call."}, 
                     {WSAEACCES:=10013, "WSAEACCES", "Permission denied."}}) 
 

ie on the second line before the first ',' we see both a definition of WSAEINTR and a reference to it.

Specifically, a ":=" operator at the top level of a {} construct on the rhs of a constant definition is treated as a nested constant definition, and obviously you cannot clash with an existing name or overwrite an existing value.

Right pleased with that, I was.

3. Re: Nested constants

• Posted by petelomax Jun 22, 2020
• 919 views

Erm, what I want is the actual constants plus three arrays, which line up by index:

constant LEFT = 331, RIGHT = 333, UP = 328, DOWN = 336, 
         KEYS  = {LEFT,RIGHT,UP,DOWN}, 
         NAMES = {"LEFT","RIGHT","UP","DOWN"}, 
         DESCS = {"move left","shift right","go up","drop down"} 

mainly so I can use idx=find() on the first sequence and then [idx] the other two, and I can't think of any way for enum to do anything beyond the top line.
(I have 61 constants in this particular set already, and from past and painful experience I know that keeping 4 such independent sets in step is no fun at all.)

The only other way I can think of that would achieve anything similar (sanely, and defining everything related side-by-side) might be something like this

sequence keys = {}, names = {}, descs = {} 
function add_key(integer key, string name, desc) 
    keys = append(keys,key) 
    names = append(names,name) 
    descs = append(descs,desc) 
    return key 
end function 
constant LEFT  = add_key(331, "LEFT",  "move left"  ), 
         RIGHT = add_key(333, "RIGHT", "shift right"), 
         UP    = add_key(328, "UP",    "go up"      ), 
         DOWN  = add_key(336, "DOWN",  "drop down"  ), 
         KEYS = keys, NAMES = names, DESCS = descs 

but with this new ":=" syntax you can just do

constant {KEYS, NAMES, DESCS} = columnize({ 
         {LEFT  := 331, "LEFT",  "move left"}, 
         {RIGHT := 333, "RIGHT", "shift right"}, 
         {UP    := 328, "UP",    "go up"}, 
         {DOWN  := 336, "DOWN",  "drop down"}}) 

All three options given would create the same seven constants, such that

?{LEFT,KEYS,NAMES,DESCS} 
-- {331,{331,333,328,336},{"LEFT","RIGHT","UP","DOWN"},{"move left","shift right","go up","drop down"}} 

Does that make more sense?

PS What's that saying? Don't worry about people stealing your ideas. If your ideas are any good, you'll have to ram them down people's throats.