+-> lambda expressions without specifying types

[Ralf Hemmecke]

If I did not make a mistake, the grammar in the Aldor User Guide seems
to allow something like x+->x+1.

But in the program below the Aldor compiler (1.1.0) cannot/does not
infer the type of the lambda expression in baz.

Stephen, is that intended or is that just a short-coming of the compiler?

Ralf

---------------------------------------------------------
 >aldor -fx -laldor aaa.as
"aaa.as", line 9:   baz(i: Integer): Integer == foo((x +-> x-1), i);
                   ...................................^
[L9 C36] #1 (Error) Expecting a comma separated list of parameters.

---rhxBEGIN aaa.as
#include "aldor"
Aaa: with {
   foo: (Integer -> Integer, Integer) -> Integer;
   bar: Integer -> Integer;
   bar: Integer -> Integer;
} == add {
   foo(f: Integer->Integer, i: Integer): Integer == f i;
   bar(i: Integer): Integer == foo((x: Integer): Integer +-> x+1, i);
   baz(i: Integer): Integer == foo((x +-> x-1), i);
}
main(): () == {
   import from String, Character, TextWriter, Integer, Aaa;
   stdout << foo(bar, 1) << newline;
   stdout << bar 1 << newline;
   stdout << bar 1 << newline;
}
main();
---rhxEND aaa.as

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[Ralf Hemmecke]

Good point, but that only allows specification of the parameter type.
I would have to give the target type anyway.

However, also

---rhxBEGIN
#include "aldor"
default x: Integer;
default y: Integer;
foo: (Integer, Integer)->Boolean == (x, y):Boolean +-> true;
---rhxEND

is not a program that the current compiler accepts.

 >aldor -fx -laldor aaa.as
"aaa.as", line 4: foo: (Integer, Integer)->Boolean == (x, y):Boolean +->
true;
                   .....................................^..^
[L4 C38] #1 (Error) Expecting a comma separated list of parameters.

Regards,
Ralf

On 03/22/2009 10:22 AM, Stephen Watt wrote:

> Yes, it allows that syntax, but it will not infer the types of the
> arguments.   The syntax makes sense, though, because the parameter
> names may have been given a default type.
>
> -- Stephen
>
> On Fri, Mar 20, 2009 at 8:14 PM, Ralf Hemmecke <ralf@...> wrote:
>> If I did not make a mistake, the grammar in the Aldor User Guide seems to
>> allow something like x+->x+1.
>>
>> But in the program below the Aldor compiler (1.1.0) cannot/does not infer
>> the type of the lambda expression in baz.
>>
>> Stephen, is that intended or is that just a short-coming of the compiler?
>>
>> Ralf
>>
>> ---------------------------------------------------------
>>> aldor -fx -laldor aaa.as
>> "aaa.as", line 9:   baz(i: Integer): Integer == foo((x +-> x-1), i);
>>                  ...................................^
>> [L9 C36] #1 (Error) Expecting a comma separated list of parameters.
>>
>> ---rhxBEGIN aaa.as
>> #include "aldor"
>> Aaa: with {
>>  foo: (Integer -> Integer, Integer) -> Integer;
>>  bar: Integer -> Integer;
>>  bar: Integer -> Integer;
>> } == add {
>>  foo(f: Integer->Integer, i: Integer): Integer == f i;
>>  bar(i: Integer): Integer == foo((x: Integer): Integer +-> x+1, i);
>>  baz(i: Integer): Integer == foo((x +-> x-1), i);
>> }
>> main(): () == {
>>  import from String, Character, TextWriter, Integer, Aaa;
>>  stdout << foo(bar, 1) << newline;
>>  stdout << bar 1 << newline;
>>  stdout << bar 1 << newline;
>> }
>> main();
>> ---rhxEND aaa.as
>>

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