Re: pass by ref

• Posted by _tom (admin) Feb 11, 2016
• 2191 views

OpenEuphoria frees you from some ideas you get by reading about programming in "other language." I wrote a tutorial to debunk ideas a beginner may have about PBR and "bigdata." A "clumsy example" now becomes a useful personal program.

_tom

OpenEuphoria vs PBR

Here are some thoughts about PBR (Pass-By-Reference) . If you program in OpenEuphoria you do not need PBR.

Pass-By-Reference

Using "other-language" the idea of PBR seems to offer:

1. speed
2. laziness
3. OOP

speed

Euphoria is fast without speed tricks like PBR. However, if your are programming in "other language" then tricks to speed things up are worthwile. Speed is the bonus you get by programming in Euphoria.

laziness

Using PBR to avoid writing an assignment statement is good for laziness and bad for safety. Unfortunately, PBR hides the exact location where the value of an object is changed in your code. Euphoria programs are easier to read and debug without PBR.

OOP

OOP style programming, while clever, can turn a simple program into a complicated program. By avoiding OOP and PBR you can keep programs simple. OpenEuphoria without PBR is friendlier.

But I Want PBR

OpenEuphoria is flexible if you insist. There is the option of using pseudo memory or structures to write powerful code. OpenEuphoria lets you write programs in your own style.

Conclusion

You don't need PBR to write efficient OpenEuphoria programs.

OpenEuphoria vs Big Data

The OpenEuphoria sequence is a marvel of language design. Go ahead and write reallybig_copy = reallybig without a speed or memory penalty because no actual copy is made. It "looks" like a copy and "behaves" like a copy but Euphoria actually uses internal pointers and optimizations to make your program fast and efficient. Go ahead and write simple--beginner--programs and let OpenEuphoria cope with "big data" effortlessly.

BigData Example

Create an enum to make indexing easier

enum Boss, Someone_else, Telno, Address, Next_meeting 

You get a set of constants numbered 1 2 3 4 5 without extra work.

You could create a huge sequence by writing:

atom hugenumber = 1_000_000 
sequence bigdata = repeat( {0,0,0,0,0}, hugenumber ) 

That gives you a database with a million items ready to be updated.

But, why bother when you can add an item just when you need it:

sequence bigdata = {} 
bigdata = append(bigdata, {"president", "", 41234, "head office", "Mon", "2:30pm" } ) 

You now have:

{ 
     {"president", "", 41234, "head office", "Mon 2:30pm" }, 
     -- room for lots more 
     $ 
} 

You are free to add, change, and remove items at any time.

Finally, use the enum constants to read and write values:

 
-- change values 
bigdata[1][Boss] = "Mr Big" 
bigdata[1][Next_meeting] = "Tue 9:00am" 
 
-- look at the values 
include std/console.e 
display( bigdata[1] ) 

You could create a procdure to output data:

procedure show( sequence data_item ) 
printf(1,  
` 

Boss            : %s 
Someone_else    : %s 
Telno           : %s 
Address         : %s 
Next_meeting    : %s 
`, data_item ) 

end procedure 

You now get output like:

show( bigdata[1] ) 

 
Boss            : Mr Big 
Someone_else    :  
Telno           : 41234 
Address         : head office 
Next_meeting    : Tue 9:00am 

A utilty to enter|change data looks like:

function write( sequence boss="", sequence someone_else="", sequence telno="", sequence address="", sequence nextmeeting="" ) 
    return { boss, someone_else, telno, address, nextmeeting } 
end function 
 
 

For example you could add a new item:

bigdata = append(bigdata, write("CEO","","","Branch Office", "Fri 3pm" ) ) 
 
display( bigdata ) 

The demo program now looks like:

enum Boss, Someone_else, Telno, Address, Next_meeting 
 
sequence bigdata = {} 
bigdata = append(bigdata, {"president", "", "41234", "head office", "Mon", "2:30pm" } ) 
 
-- change values 
bigdata[1][Boss] = "Mr Big" 
bigdata[1][Next_meeting] = "Tue 9:00am" 
 
-- look at the values 
include std/console.e 
display( bigdata[1] ) 
 
/* 

{ 
  "Mr Big", 
  "", 
  41234, 
  "head office", 
  "Tue 9:00am", 
  "2:30pm" 
} 
*/ 
 
 
procedure show( sequence data_item ) 
printf(1,  
` 

Boss            : %s 
Someone_else    : %s 
Telno           : %s 
Address         : %s 
Next_meeting    : %s 
`, data_item ) 

end procedure 
 
show( bigdata[1] ) 
 
/* 

Boss            : Mr Big 
Someone_else    :  
Telno           : 41234 
Address         : head office 
Next_meeting    : Tue 9:00am 
*/ 
 
 
--A utilty to enter|change data looks like: 
function write( sequence boss="", sequence someone_else="", sequence telno="", sequence address="", sequence nextmeeting="" ) 
    return { boss, someone_else, telno, address, nextmeeting } 
end function 
 
 
--For example you could add a new item: 
bigdata = append(bigdata, write("CEO","","","Branch Office", "Fri 3pm" ) ) 
 
display( bigdata ) 
 
/* 

 { 
    "Mr Big", 
    "", 
    "41234", 
    "head office", 
    "Tue 9:00am", 
    "2:30pm" 
  }, 
  { 
    "CEO", 
    "", 
    "", 
    "Branch Office", 
    "Fri 3pm" 
  } 
} 
*/ 

Conclusion

You can create a small database program for yourself, with unlimited capacity and flexibility, with very little code.