OpenEuphoria

1. Phix wiki 2

• Posted by _tom (admin) Jan 24, 2021
• 775 views
• Last edited Jan 25, 2021

Routines

There are three kinds of routines: procedure, function, and type. A procedure does not return a value, a function returns a value, and a type declares and tests user defined data-types.

-- this is for action 
procedure hello() 
    ? "hello" 
    end procedure 
 
hello() 
 
-- outputs: 
// hello 
 
-- this returns a value 
function pi() 
    return 3.14 
    end function 
 
    -- use a function in an expression 
    ? pi()*4*4 
    //  50.24 
 
    -- explicit discard is needed to ignore return 
    {} = pi() 
 
-- this creates a user data-type 
type positive(number x ) 
    if x >= 0 then return 1 
    else return 0 end if 
    end type 
 
    -- use to declare a variable 
    positive ndx = 5 
 
    -- use to enforce type-checking 
    ndx = -2 
    //  type-check error 

A function declared as part of a class works like a method in OOP style programming.

Having both procedure and function enables the interpreter to display more meaningful error messages.

Symmetrical Indexing

From a discussion on the Julia website "What’s the big deal? 0 vs 1 based indexing" comes a simple explanation:

Steven_Sagaert Dec 2016 
 
That’s exactly it. 
1-based indexing is actual indexing like in mathematics, 
while 0-based “indexing” isn’t indexing at all but pointer arithmetic. 
This comes from C where an array is just syntactic sugar for a pointer. 

In symmetrical indexing items are numbered from `1` to `n` (where `n` is equal to the length of the sequence). Items can also be indexed using negative values: `-n` is the first item and `-1` is the last item.

   string   txt = "hello" 
?   txt[-1]       // 'o' 
?   txt[3..4]     // "ll" 
 
            --      symmetrical indexing 
   sequence dta = { 1, 2, "cat", {20,2} } 
            --      1  2    3      4 
            --     -4 -3   -2     -1 
 
                      ? dta[ 3.. 4]   // {"cat",{20,2.2}} 
                      ? dta[-2..-1]   // {"cat",{20,2.2}} 

• one-based indexing is intuitive
• index values are used for slicing
• intuitive symmetrical indexing and slicing
• the value zero is an obvious indexing error
• the value zero can be used for item not found
• 0'th location is a virtual head
• n+1'th location is a virtual tail

https://discourse.julialang.org/t/whats-the-big-deal-0-vs-1-based-indexing/1102

Generic operators

Operators are generic:

-- the + operator always adds 
 
atom chr = 'T' 
    ? chr + 32  // 't' 
 
atom x = 100 
    ? x + 32    // 132 
 

Operators can span strings and sequences:

string txt = "HELLO" 
    ? sq_add( txt, 32 )      // "hello" 
 
sequence dta = { 2, 9, 34 } 
    ? sq_mul( dta, 100 )     // {200,900,3400} 

Generic routines

Sequences and strings behave alike:

string txt = "Have a nice day" 
 
? sort(txt)                       // "   Haaacdeeinvy" 
? shuffle(txt)                    // "dnve  aaiecH ya" 
? reverse(txt)                    // "yad ecin a evaH" 
 
sequence lst = { "hamster", "dog", "fish", "cat"  } 
 
? sort(lst)                       // {"cat","dog","fish","hamster"} 
? shuffle(lst)                    // {"fish","dog","cat","hamster"} 
? reverse(lst)                    // {"cat","fish","dog","hamster"} 

You can use the same skills for any kind of data values.

Equivalence of strings and sequences

Each character is represented by a number value. A string is actually a sepecial case of a sequence.

? sq_sqrt( "Hello" ) 
    // {8.485281374,10.04987562,10.39230485,10.39230485,10.53565375} 
 
? sq_sqrt( {'H','e','l','l','o'} ) 
    // {8.485281374,10.04987562,10.39230485,10.39230485,10.53565375} 
 
? sq_sqrt( {72, 101, 108, 108,111 } ) 
    // {8.485281374,10.04987562,10.39230485,10.39230485,10.53565375} 

3. Re: Phix wiki 2

• Posted by _tom (admin) Jan 24, 2021
• 740 views

   string   txt = "hello" 
 
? txt[3..4] // "lo" 

both - - and / / are line comments in phix

_tom

5. Re: Phix wiki 2

• Posted by irv Jan 24, 2021
• 746 views

"A procedure is packages action," doesn't make a lot of sense.

7. Re: Phix wiki 2

• Posted by petelomax Jan 27, 2021
• 663 views

atom chr = 'T'  
    ? chr + 32  // 't'  

Erm yeah, but the output is 116...