October 19, 2004

Next language will be Prolog -- download SWI prolog from the Web or GNU prolog

There will be another Ada program to write.

Additional notes about example programs

when you output an integer in Ada, it uses a default width

ada.integer_text_io.put (6);

ada.integer_text_io.put (item => 6); -- this statement is identical to the statement above9

alternatively, you can control the number of spaces it uses

ada.integer_text_io.put (item => 6, width => 5);

=> is called an arrow in Ada

<> is called a box in Ada

-- Ada’s predefined subtype positive

subtype positive is integer range 1.. integer’last;

The ada String type is declared as an unconstrained array of characters;

-- Ada’s predefined type string

Type string is array (positive range <>) of character;

-- a declaration of a string variable in Ada

-- when a string variable is declared it must be constrained

-- lowest index allowed is 1 because declaration specifies that the range is positive

MyName : string(1..5);

-- a declaration of a string constant -- doesn’t require specification of range. Range is taken from declaration

MyConstantString : constant String := “however many characters in this string”;

-- a number of the examples show Ada’s exception handling capabilities

-- user can define own exceptions

-- exceptions in Ada are raised

-- exception handlers begin with the reserved word exception

-- each individual handler begins with the reserved word when

-- after an exception is handled, control leaves the block in which the exception occurred which is why if the exception handler is inside a loop and

-- you don’t want to leave the loop after handling the exception you need a begin end pair around it