Re: Introspection?

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axtens_bruce said...

Is there any way for Hello to be able to see its own name so that one might code

This is somewhat supported by using call_stack() from euphoria/debug/debug.e, the same way I demonstrated for variable_id. (These routines need more documentation for the 4.2 release.)

But it's only available in the interpreter and things can get weird if the interpreter inlines a call, which will be left out of the stack (you can disable this using without inline for a small performance loss).

Here's an example that sort-of recreates the C preprocessor macros like __LINE__ and __FILE__ (although they're functions here since we don't have macros per se).

include euphoria/debug/debug.e 
-- cs[1] is call_stack() itself 
-- cs[2] is the calling routine 
function __FUNC() 
    sequence cs = call_stack() 
    return cs[2][CS_ROUTINE_NAME] 
end function 
function __FILE() 
    sequence cs = call_stack() 
    return cs[2][CS_FILE_NAME] 
end function 
function __LINE() 
    sequence cs = call_stack() 
    return cs[2][CS_LINE_NO] 
end function 
-- heck, let's throw date and time in there too! 
constant MONTH = {"Jan","Feb","Mar","Apr","May", 
function __DATE() 
    sequence d = date() 
    d[1] = d[1] + 1900 
    d[2] = MONTH[d[2]] 
    return sprintf( "%s %02d %d", {d[2],d[3],d[1]} ) 
end function 
function __TIME() 
    sequence d = date() 
    return sprintf( "%02d:%02d:%02d", d[4..6] ) 
end function 
procedure Hello(sequence place) 
    printf(1, "%s %s ", {__DATE(),__TIME()}) 
    printf(1, "%s:%d ", {__FILE(),__LINE()}) 
    printf(1, "%s, %s!\n", {__FUNC(),place}) 
end procedure 


$ eui /tmp/demo.ex 
Mar 16 2023 11:32:05 /tmp/demo.ex:21 Hello, World! 

axtens_bruce said...

I can't think of a good reason right now for that ability. Just curious.

I can: logging! I make heavy use of this feature in mvc/logger.e which will be ported to the standard library for Euphoria 4.2.

Right now you'd use it like this:

function max( atom x, atom y ) 
    log_trace( "x=%g, y=%g", {x,y} ) 
    return 0 
end function 
? max( 2, 3 ) 

Then call the interpreter with -D LOG_TRACE and get some fancy output complete with colored text (if writing to STDOUT or STDERR).

$ eui -D LOG_TRACE /tmp/demo.ex 
2023-03-16 11:20:00 TRACE max@/tmp/demo.ex:2 x=2, y=3 

In fact I should be able to combine that with what I demonstrated for variable_id() to provide cleaner and simpler per-call logging. Stay tuned for that.


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