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English

New Programming Language Invented

Hermetic Systems has released an interpreter for a new programming language called EDC which is designed for operations on and with calendar dates, such as date arithmetic and conversions from dates in one calendar to another.

EDC is an interpreted language. Programs are written with any text editor and are saved in normal text files. When such a source code file is read by the interpreter (the Advanced Version of the "Easy Date Converter" software published by Hermetic Systems) it is executed line-by-line, with results output to a text window in the software.

EDC is an untyped programming language; all variables store numbers. There is, however, a conceptual difference between "date" variables and others. A "date" variable is a variable whose value is regarded by the programmer as holding a Julian day number (which is a number of days elapsed since January 1st, 4713 BCE, in the Julian Calendar).

When values are assigned to date variables a calendar designation may be appended, e.g., "date_iso = 2002-05-3 ISO". Calendars currently supported are the Common Era Calendar (a.k.a. the Gregorian Calendar), the Julian Calendar, the ISO Week Calendar and two forms of the Hermetic Leap Week Calendar. Dates may also be designated as ordinal (day-in-year) dates and as Julian day numbers.

A problem when processing dates is that they are written in different formats in different countries. The main difference is that in the U.S. dates are typically written in the form "1/31/2008" whereas in most other countries they are written in the form "31-1-2008" or "31.1.2008". To allow dates to be expressed in different formats EDC supports a statement of the form "date format =" followed by one of: Y-M-D, D-M-Y, M-D-Y, Y/M/D, D/M/Y, M/D/Y, Y.M.D, D.M.Y and M.D.Y.

The following keywords are used to control the order in which statements are executed: IF, THEN, IFNOT, ELSE, ELSEIF, ELSEIFNOT, ENDIF, DO, EXITDO, ENDDO, SKIP, NOSKIP, STOP. These are all used in the usual way, except that the keywords IFNOT and ELSEIFNOT are unusual, but their use is intuitive.

The interpreter in the software outputs results to a text window by means of the "output:" statement. The value of a numerical variable is output using the Val() function, and of a date variable using the DateVal() function, e.g., "output: Val(year)".

The principal means of input is the program being processed, in which variables are initialized. It is also possible to obtain input from a user while a program is running. This is done by means of an "input:" statement, which opens a dialog box to obtain a numerical value or a date.

In addition to the two functions Val() and DateVal(), which are intended only for use with the "output:" statement, there are currently about a dozen built-in functions. These include functions for (a) adding and substracting numbers and dates (e.g., to obtain the number of days between two dates), (b) getting the day of the week (e.g., Friday) for a particular date, (c) getting the number of the day, week, month or year of a given date in a given calendar, (d) ascertaining whether a year in a given calendar is a leap year and (e) gettting the date of new years day for a given year in a given calendar.

The EDC programming language supports user-defined functions and subroutines. Functions have the usual properties one expects in a programming language, such as that a function definition can include calls to other functions.

For more information about EDC and its interpreter, the "Easy Date Converter Advanced Version" software, see http://www.hermetic.ch/edca/edca.htm. Numerous examples of programs written in EDC are given at http://www.hermetic.ch/edca/functions.htm and associated web pages.