[erlang-questions] difference between "," and "andalso" in guards

[Adel Zhang]

hi, I am currently reading "learnyousomeerlang". In "Syntax in Functions"  
chapter "guards" section, Fred said

<quote>
Note: I've compared , and ; in guards to the operators andalso and orelse.  
They're not exactly the same, though. The former pair will catch  
exceptions as they happen while the latter won't. What this means is that  
if there is an error thrown in the first part of the guard X >= N; N >= 0,  
the second part can still be evaluated and the guard might succeed; if an  
error was thrown in the first part of X >= N orelse N >= 0, the second  
part will also be skipped and the whole guard will fail.
</quote>

So I write a codesnippet:

-module(g).
-export ([right_age/1, right_age_2/1, right_age_3/1]).

right_age(X) when X >= 16, X =< 104 ->
	true;
right_age(_) ->
	false.


right_age_2(X) when (X >= 16) andalso (X =< 104) ->
	true;
right_age_2(_) ->
	false.

right_age_3(X) when (X >= 16) and (X =< 104) ->
	true;
right_age_3(_) ->
	false.


And compile with 'S' option to get the assembly code as follow:

{function, right_age, 1, 2}.
   {label,1}.
     {line,[{location,"g.erl",4}]}.
     {func_info,{atom,g},{atom,right_age},1}.
   {label,2}.
     {test,is_ge,{f,3},[{x,0},{integer,16}]}.
     {test,is_ge,{f,3},[{integer,104},{x,0}]}.
     {move,{atom,true},{x,0}}.
     return.
   {label,3}.
     {move,{atom,false},{x,0}}.
     return.


{function, right_age_2, 1, 5}.
   {label,4}.
     {line,[{location,"g.erl",10}]}.
     {func_info,{atom,g},{atom,right_age_2},1}.
   {label,5}.
     {test,is_ge,{f,6},[{x,0},{integer,16}]}.
     {test,is_ge,{f,6},[{integer,104},{x,0}]}.
     {move,{atom,true},{x,0}}.
     return.
   {label,6}.
     {move,{atom,false},{x,0}}.
     return.


{function, right_age_3, 1, 8}.
   {label,7}.
     {line,[{location,"g.erl",15}]}.
     {func_info,{atom,g},{atom,right_age_3},1}.
   {label,8}.
     {test,is_ge,{f,9},[{x,0},{integer,16}]}.
     {test,is_ge,{f,9},[{integer,104},{x,0}]}.
     {move,{atom,true},{x,0}}.
     return.
   {label,9}.
     {move,{atom,false},{x,0}}.
     return.



Apparently the three version right_age function assembly code are almost  
same. It confuse me totally.

1) can assembly code tell the function behaviour difference?
2) what does {f,6} {x,0} in assembly code mean?
3) how can I verify Fred's statement?