Saturday, January 9, 2010

DTREG Defines Implicit Global Variables In The DTL Program

Program Online
DTL is a language programing that built easy to generate new variables, transform and combine input variables and select records to be used in the analysis.

Using it, you can manage data being analyzed, generate new variables as a function of input variables and select which records are used in an analysis.
Although DTL does not have all of the features of languages such as C and Visual Basic you will find that it is a rich language unto itself and includes features not commonly found in other languages such as fully dynamic string variables and a wide selection of built-in library functions.

The syntax of the DTL language is intentionally similar to that of the C programming language.
If you have prior experience programming in C you will be able to begin using DTL almost immediately.

The following list summarizes the major differences between C and DTL:

• DTL does not have structures or pointers.
• Arguments to functions are passed by copying. On entry the values of calling arguments are copied to the receiving formal parameters. On exit, the values are copied back to the calling arguments.
• DTL supports three data types: int (32-bit integer), double (64-bit floating point), and string (variable length strings).
• The DTL string data type provides fully dynamic strings whose size is determined at execution time rather than by statement declaration. DTL strings can store binary data including the null character.
• DTL provides a substring operator for extracting or changing a portion of a string. There is also a string concatenation operator (‘$’).
• DTL supports one and two-dimensional arrays. The syntax for declaring the array size and for subscripting elements has the form “array[sub1,sub2]” rather than the C convention of “array[sub1][sub2]”. A “resize” function can be used to change the size of an array during the execution of a program. When arrays are passed to functions the size of the array in the function “conforms” to the size of the passed array. Library functions are provided to determine the actual size of an array.
• DTL is very “liberal” with regard to type conversions. Any type of variable may be assigned to any other. Any type of variable or expression may be used as an argument to a function without regard to the type of the formal parameter. String and numeric values may be used together in expressions.