Re: FLI type error

Yes, so do I. But I was asking about type inference in LW FLI (aka unification). I don’t think LW has type inference capabilities. There can be some weak inference capabilities in the conversion of Lisp strings to FLI:CHAR pointers. But I think that comes about by having defined convertors, not naturally part of the FLI, but an augmentation provided by Martin and company…


> On Mar 7, 2026, at 12:14, Paul Werkowski <[email protected]> wrote:
> 
>  I get "Hello".
> 
> On 3/7/2026 2:11 PM, David McClain wrote:
>> (coerce "Hello" 'base-string)
>> 
>> But, is LW smart enough to see the transitive closure from GLCHAR to BASE-CHAR?
>> 
>>> On Mar 7, 2026, at 12:08, Paul Werkowski (as pw at snoopy dot qozzy dot com) <[email protected]> wrote:
>>> 
>>> No, *default-character-element-type* is BASE-CHAR.
>>> 
>>> On 3/7/2026 2:04 PM, David McClain wrote:
>>>> Web search shows GLCHAR is 8-bit char (ASCII ?). We had 30+ years of stability and simplicity once EBCDIC gave way to ASCII.
>>>> 
>>>> But my recent experience with the Rust world shows that simplicity is no longer relevant. Very possibly you are using Wide Lisp chars instead of BASE-CHAR?
>>>> 
>>>> 
>>>> 
>>>>> On Mar 7, 2026, at 11:24, Paul Werkowski (as pw at snoopy dot qozzy dot com) <[email protected]> wrote:
>>>>> 
>>>>> Well, GLCHAR is lisp :char. I see that the FLI manual has things like convert-to-foreign-type etc. I shall poke around in there for awhile.
>>>>> 
>>>>> Thanks for the suggestion,
>>>>> PW
>>>>> 
>>>>> On 3/7/2026 12:43 PM, David McClain wrote:
>>>>>> No… I  now see.
>>>>>> 
>>>>>> It appears that Lisp cannot automatically convert your Lisp string to the required C type (:POINTER OPENGL:GLCHAR). There has always been a sometimes conversion ability to allow Lisp strings to become C strings. But your required type is not a “C String” kind of pointer.
>>>>>> 
>>>>>> Yes, even though it probably really is a C string type, I have no idea whether OPENGL:GLCHAR is a 8-bit ASCII char, or a Unicode wide char, etc. So probably no implicit LW conversions would apply.
>>>>>> 
>>>>>> IOW… you probably now have to provide your own explicit conversions.
>>>>>> 
>>>>>> - DM
>>>>>> 
>>>>>>> On Mar 7, 2026, at 10:37, David McClain <[email protected]> wrote:
>>>>>>> 
>>>>>>>> Both of these get a runtime error
>>>>>>>> "aPos"  (and "triangleColor") cannot be converted to foreign type
>>>>>>>> (:POINTER   OPENGL:GLCHAR).
>>>>>>>> 
>>>>>>> Offhand… did the OpenGL API change since 10 years ago? Perhaps now expects an array of char, or a string pointer?
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>>> On Mar 7, 2026, at 09:59, Paul Werkowski (as pw at snoopy dot qozzy dot com) <[email protected]> wrote:
>>>>>>>> 
>>>>>>>> I'm looking at some code from 5-10 years ago, experimenting with OPENGL, that uses the LW example code to setup the interface. The icosahedron example works fine so no issue there.
>>>>>>>> 
>>>>>>>> Here are two fragments from my code.
>>>>>>>> 
>>>>>>>> (let ((pos-attr (gl-get-attrib-location shader-pgm "aPos"))
>>>>>>>> 
>>>>>>>> (let((unicolor (gl-get-uniform-location
>>>>>>>>                            shader-pgm "triangleColor")))
>>>>>>>> 
>>>>>>>> Both of these get a runtime error
>>>>>>>> "aPos"  (and "triangleColor") cannot be converted to foreign type
>>>>>>>> (:POINTER   OPENGL:GLCHAR).
>>>>>>>> 
>>>>>>>> GLCHAR is defined in opengl/types.lisp as
>>>>>>>> 
>>>>>>>> (fli:define-c-typedef (glchar (:foreign-name "GLchar"))
>>>>>>>>  :char)
>>>>>>>> 
>>>>>>>> Same issue with both LWW 8.1.2 64 bit and 7.1.2 32 bit.
>>>>>>>> 
>>>>>>>> This all used to work. What could be wrong???
>>>>>>>> 
>>>>>>>> Puzzled again,
>>>>>>>> Paul
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
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