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built-in functions


    This subchapter looks at built-in functions.

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built-in functions

    This subchapter looks at built-in functions.

    Built-in functions provide a wide variety of useful capabilities. While this chapter is about calculations and most programming languages have a rich set of built-in functions for calculations, built-in functions have much wider uses.

    Most programming languages invoke a built-in function by giving the name of the built-in function followed by any input. The inputs are usually placed inside parenthesis, but this varies by language. Most languages treat the output of a built-in function in much the same manner as fetching the value of a variable and typically a built-in function can be placed anywhere in an expression that a variable of the same kind could be placed. The results of the built-in function usually can be used in assignments and computations.

    The form would typically look something like:

    a := abs(b);

    In the example, the built-in function takes the value of the variable a, finds its absolute value, and then assigns the answer to the variable b.

    The following discussion of JOVIAL (an old programming language) gives the flavor of the kinds of uses for built-in functions.


    The following material is from the unclassified Computer Programming Manual for the JOVIAL (J73) Language, RADC-TR-81-143, Final Technical Report of June 1981.

    1.1.5 Built-In Functions

    The JOVIAL built-in functions provide advanced, specialized
    operations that are not covered by the JOVIAL operators.  They
    are summarized in the following table:

         Function       result

         LOC(x)         A pointer to the object referenced by r

         NEXT(p,i)      A pointer to the i'th data object after
                        the one selected by p
         NEXT(s,i)      The i'th status value after status value s

         BIT(b,i,n)     A string of n bits starting at the i'th bit
                        of the bit string b
         BYTE(c,i,n)    A string of n characters starting at the i'th
                        character of the character string c

         SHIFTL(b,n)    Bit string b shifted left by n bits
         SHIFTR(b,n)    Bit string b shifted right by n bits

         ABS(x)         Absolute value of x
         SGN(x)         +1, 0, or -1 for x>0, x=0, x<0

         BITSIZE(x)     Logical size of x in bits
         BYTESIZE(x)    Logical size of x in bytes
         WORDSIZE(x)    Logical size of x in words

         LBOUND(t,d)    Lower bound of d'th dimension of the table t
         UBOUND(t,d)    Upper bound of d'th dimension of the table t

         NWSDEN(t)      Number of bytes allocated to each entry of
                        the table t

         FIRST(s)       First status value in status list for s
         LAST(s)        Last status value in status list for s

    An example of the use of a built-in function is:

         C = BYTE("ABCDEF",2,3);

    The built-in functions extracts "BCD" from the string "ABCDEF".

    Chapter 1 Introduction, page 9

free music player coding example

    Coding example: I am making heavily documented and explained open source code for a method to play music for free — almost any song, no subscription fees, no download costs, no advertisements, all completely legal. This is done by building a front-end to YouTube (which checks the copyright permissions for you).

    View music player in action:

    Create your own copy from the original source code/ (presented for learning programming).

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