Re: Ada and string literals

[ake.ragnar.dahlgren@gmail.com]

On Wednesday, January 30, 2013 12:50:38 PM UTC+1, Mart van de Wege wrote:
> Niklas Holsti <niklas.holsti@tidorum.invalid> writes: > On 13-01-30 02:44 , codeallergy wrote: >> hi comp.lang.ada, >> >> question from a newcomer: Why ada does not allow using a string >> literal with access type ? >> >> abc : access string := "LITERAL"; -- error. > > Because, unlike C, Ada does not confuse arrays with pointers. > > This is the closest Ada equivalent: > > Literal : aliased constant String := "LITERAL"; > abc : access constant String := Literal'Access; More importantly, I cannot see why you would want an access to a string literal. Just use the string literal as a normal parameter, and let the compiler worry about how to handle that. Mart -- "We will need a longer wall when the revolution comes." --- AJS, quoting an uncertain source.

The other day I was looking at the Ada code for the GPS (GNAT Programming Studio). This is code taken from the procedure GPS.Main:

subtype String_Access is GNAT.Strings.String_Access;

Home                   : String_Access;
Home_Dir               : Virtual_File; 
Project_Name           : Virtual_File := No_File; 
Prefix                 : String_Access;
Prefix_Dir             : Virtual_File; 
GPS_Home_Dir           : Virtual_File; 
Batch_File             : String_Access; 
Batch_Script           : String_Access; 
Tools_Host             : String_Access; 
Target                 : String_Access; 
Protocol               : String_Access; 
Debugger_Name          : String_Access; 
Startup_Dir            : String_Access; 
About_Contents         : String_Access;
 
The string access type was chosen over the string type for handling strings. Maybe to avoid setting a maximum string length? Performance reasons? Anyways, I think the authors of the GPS are able to give a good motivation of when one prefers the string access type over the ordinary string type.

Best regards,
Åke Ragnar Dahlgren