M THE MODELING LANGUAGE in Font

Painting PDF 417 in Font M THE MODELING LANGUAGE

Types do not necessarily need to be named in M. You could define an anonymous type by simply enumerating a collection. For instance, the unnamed collection in Listing 5-1 could be treated as a perfectly valid type in M, since it is an expression that returns a set of values. Listing 5-1. An Anonymous Type { "Red", "Green", "Blue" } One might ask, Could you have an instance of Car and an instance of Boat (if defined with the same structure as that of the Car type) that are equivalent The answer is yes. If you refined the two types, say by adding a WheelBase : Decimal19 attribute to the Car type definition and a PropType : Text to the Boat type definition, then the two types would no longer have the same structure, and the answer would be no.

Table 5-1 lists all of the intrinsic types included in the M language. If you ve used typed programming languages, nearly all of these types (numbers, dates, times, text, logical, and binary) and their operators should be familiar to you. The last two types listed in this table, Collection and Entity, are particularly important in M because of its modeling orientation, and will be given further treatment throughout this chapter. Table 5-1. M Intrinsic Types

All possible values. All possible values except the Entity and Collection types. Any numeric value. A fixed point or exact number. A fixed point or exact number. A fixed point or exact number.

Decimal28 Decimal38 Integer Integer8 Integer16 Integer32 Integer64 Scientific Single Double Unsigned Unsigned8 Unsigned16 Unsigned32 Unsigned64 Date DateTime DateTimeOffset Time Text Logical Binary Guid

A fixed point or exact number. A fixed point or exact number. A signed integer. A signed integer with fewer than 9 bits of precision. A signed integer with fewer than 17 bits of precision. A signed integer with fewer than 33 bits of precision. A signed integer with fewer than 65 bits of precision. A floating-point or exact number. A 32-bit floating-point or exact number. A 64-bit floating-point or exact number. An unsigned integer. An unsigned integer with fewer than 9 bits of precision. An unsigned integer with fewer than 17 bits of precision. An unsigned integer with fewer than 33 bits of precision. An unsigned integer with fewer than 65 bits of precision. A calendar date. A calendar date and time of day independent of time zone. A calendar date and time of day within a specific time zone. A time of day and time zone. A sequence of characters. A logical flag. A sequence of binary octets. A globally unique identifier

A single binary octet. An unordered group of potentially duplicate values. A collection of labeled values.

The collection type is an unordered group of potentially duplicate values. A collection can be constructed as an expression with a beginning brace ({), a type reference, an optional multiplicity (described shortly), and an ending brace (}). So the following examples are all valid collections: { NPR , ABC , CBS , NBC } names { Red , White, Blue } // a collection of four broadcast network // a collection of three color names // a collection of three ball

{3.141, 2.718} // the collection of the two transcendental numbers and e, expressed to a 3-decimal precision {Integer#8} {Unsigned16#1..8} {Date#4..} {Single*} {Double+} // a collection of any eight integers // a collection of one to eight Unsigned16 integers // a collection of four or more Date types // a collection of zero or more 32-bit floating point numbers // a collection of one or more 64-bit floating point numbers

Cars : {Car*} // defines the Cars extent as the collection of all values of the Car derived type { Red , 32, { }, NPR } // defines a collection with two text values, an integer value, and an empty collection value

The last example in the preceding list shows that the elements of a collection do not necessarily have to be of the same type, and that collections can contain other collections. The next to last expression uses the ascription operator (:), (as in, ascribe this identifier to this type ) to define the Cars extent. I ll talk about this in the section titled Extents. Note that the definition of the collection type said that the collections can have duplicate values. So the collection {1, 2, 3, 1, 1, 3, 4, 98} would conform to an {Integer}#8 definition because it is a collection of eight integers, though with some duplicates. Collections also have no positional or sequential information (unlike lists), so the following expression would be true: {1, 2, 3, 4} == {4, 1, 3, 2}.