[Oberon] Modula2 vs Oberon IMPORT

[Chris Burrows]

> -----Original Message-----
> From: Jan Verhoeven [mailto:jan at verhoeven272.nl] 
> Sent: Sunday, 9 January 2011 3:17 AM
> To: ETH Oberon and related systems
> Subject: Re: [Oberon] Modula2 vs Oberon IMPORT
> 
> 
> Yes but it will not add clarity to your sources. Unless you 
> use a silly 
> kind of importing:
> 
> PROCEDURE ReadString (string : ARRAY OF CHAR);
> 
> IMPORT In.ReadString;
> 
> BEGIN
>    In.ReadString (string)
> END ReadString;
> 
> I'm not sure if the IMPORT in this example will be accepted by all 
> compilers.
> 

I don't know any Oberon compiler that would accept the above, but every
Oberon compiler should compile the following (assuming In is an available
import):

  MODULE M;

  IMPORT In;

  PROCEDURE ReadString(VAR string: ARRAY OF CHAR);
  BEGIN
    In.ReadString(string)
  END ReadString;

  END M.


I have seen this technique used in ETH code and it can help to remove
clutter e.g.

    CASE reg OF
      FP : WrStr("FP")
      | SP : WrStr("SP")
      | LR : WrStr("LR")
      | PC : WrStr("PC")
      | CPSR : WrStr("CPSR")
      | SPSR : WrStr("SPSR")
    ELSE
      WrChar('R'); WrInt(reg)
    END

instead of:

    CASE reg OF
      FP : Texts.WriteString(w, "FP")
      | SP : Texts.WriteString(w, "SP")
      | LR : Texts.WriteString(w, "LR")
      | PC : Texts.WriteString(w, "PC")
      | CPSR : Texts.WriteString(w, "CPSR")
      | SPSR : Texts.WriteString(w, "SPSR")
    ELSE
      Texts.WriteChar(w, 'R'); Texts.WriteInt(w, reg)
    END

Chris.