Using code blocks, again

Using code blocks again (.pdf)

Array and GET tricks

Array and GET tricks

The secrets of array handling, part 2.

The secrets of array handling Part – 2

What a preprocessor is ?

What a preprocessor is, how will operate, and what benefits it will offer ?

Let’s Look at Clipper 5.0’s preprocessor

C5 Preprocessor

What a preprocessor is, how will operate, and what benefits  it will offer ?

Clipper 5.0’s Preprocessor

UDFs_02 : Calling by reference

/*

UDFs_02 : Calling by reference

In the previous example “cCurrent” was an “argument” ( or actual parameter ), in caller side. In called (invoked / recevied ) side “cTime” is a parameter ( or “formal” parameter).

Though two variables has same value (at the beginning of called function), nothing changed in these definitions, though if two variables has the same name.

In the previous example, “cCurrent” passed by value by caller and “cTime” is a “local” variable as a (“formal”) parameter. So, after terminated the “AmPm” function, “cTime” too erased from memory and became inaccessible.

There is one another method: passing by reference. In this method, caller routine passes (sent) the argument by its reference, not value. In this case called routin uses this formal parameter by its reference, can change  its value and after termination of called routine, argument left alive for caller.

For passing an argument by reference only requirement is adding a “@” sign at the beginning of variable name: AmPm( @cCurrent ), instead of AmPm( cCurrent ).

In this case we haven’t need a return value by called routine, and so called routine haven’t being a FUNCTION.

For more information refer here:

*/

PROCEDURE Main()
cCurrent := "01:43" 

 AmPm( @cCurrent )

 ? cCurrent

 WAIT

RETURN // Main()
*-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.
PROCEDURE AmPm( cTime )
IF VAL( cTime ) < 12
 cTime += " am"
 ELSEIF VAL( cTime ) = 12
 cTime += " pm"
 ELSE 
 cTime += STR( VAL( cTime ) - 12, 2 ) +;
 SUBSTR( cTime, 3 ) + " pm"
 ENDIF

RETURN // AmPm()
*-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.