[mercury-users] record field access syntax

[Simon Taylor]

On 06-Jan-2002, Dave Slutzkin <dave_slutzkin at yahoo.com> wrote:
> main -->
>     { T = test(1,2) } ,
>     { T ^ one := 3 } ,
>     print(T ^ one) , nl.
> 
> Why do I get this error message?
> 
> test2.m:021: Error: expected `Field =^ field1 ^ ... ^
> fieldN'
> test2.m:021:   or `^ field1 ^ ... ^ fieldN := Field'.
> test2.m:021:   in DCG field access goal.
> 
> If I'm reading it right, this should work as well:
> 
> main -->
>     { T = test(1,2) } ,
>     { 'one :='(T,3) } ,
>     print(T ^ one) , nl.
> 
> In this instance I get `undefined predicate 'one
> :=/2''.
  
The function 'one :=/2' doesn't do destructive update,
it returns a modified copy.

	main -->
		{ T0 = test(1,2) } ,
		{ T = T0 ^ one := 3 } ,
		print(T ^ one) , nl.

Simon.
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