Re: Declaration design preference: type or name first

On 30 Okt., 14:25, James Harris <james.harri...@[EMAIL PROTECTED]
> wrote:
> Some examples just to illustrate the point, not in a final form:
>
> Name first
>    var fred <integer>
>    var freda <integer> = 0
>    var char_value <integer 8>
>    var ages <array (0 ... 150) of <integer>>
>    var x, y = 2, z <float>
>
> Type first
>    var <integer> fred
>    var <integer> freda = 0
>    var <integer 8> char_value
>    var <array (0 ... 150) of <integer>> ages
>    var <float> x, y = 2, z
Years ago I came to the conclusion that the "type first"
notation is better. Therefore I choosed it for Seed7.
The advantage is that all declarations can be written
in a similar way:

Variable declaration:

  var integer: number is 0;

Constant declaration:

  const float: radianToDegrees is 57.295779513082320876798154814114;

Type declaration:

  const type: myInteger is integer;

Parameter declaration:

  in float: x

Function declaration:

  const func float: sinD (in float: x) is
    return sin(x * degreesToRadian);

Each declaration can be identified with a keyword:

  const  -- Constant declaration
  var    -- Variable declaration
  in     -- Ingoing parameter (may be 'val' or 'ref')
  inout  -- Reference parameter which goes in and out
  ref    -- Constant reference parameter
  val    -- Constant value parameter
  in var -- Variable value parameter

After the introducing keyword a type is required.
Compared to the C declaration this is a big advantage.
If the type is undefined or spelled wrong the compiler
still knows that he is processing a declaration.

The use of the colon and the 'is' keyword make it
easier to parse a declaration (for humans and computers).

I decided to use the 'is' keyword instead of = or :=
because an initializing operation is not an assignment.
When you initialize a variable or constant it gets its
value for the first time (before that it had an undefined
value). OTOH an assignment can assume that a variable
has already a legal value (e.g.: A pointer which points
to allocated memory which can be used or resized).

Greetings Thomas Mertes

Seed7 Homepage:  http://seed7.sourceforge.net
Seed7 - The extensible programming language: User defined statements
and operators, abstract data types, templates without special
syntax, OO with interfaces and multiple dispatch.