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D - Some wierd error messages that probably could make more sense, and

reply SL <shadowlord13 users.sourceforge.net> writes:
These are some weird error messages I've gotten that could probably make 
more sense if changed, and also a few things that could possibly use 
tweaking (and issues with calling overloaded functions, apparently):

'yearStr.length' is not an lvalue

Got that one from trying to do somearray.length+=1; (or -=, etc)
So I had to do somearray.length=somearray.length+1; instead, which is 
not too much of a hassle, but is weird. Also note that there was no 

make sense to someone who doesn't know what an lvalue is (AFAIK it's 
something that can be on the left hand side of an =, which 
somearray.length SHOULD be, I would think) or thinks it IS an lvalue and 
the compiler is wrong. So it's not exactly easy to track down and figure 
out (the first time you get it anyways, after that you know what to look 
for).

spacesim.d(205): Array operations not implemented

I got that one when I tried doing someString+someOtherString. I had 
momentarily forgotten I was supposed to use ~, and it took me a few 
seconds to figure out what the problem was, because the error message 
looked like something totally different. A clearer message, such as "Use 
the ~ operator to concatenate strings, not +" would help when 
(inevitably) people try to use + with strings.

Also, toString(someNumberTypeHere) doesn't work when trying to use it 
from a class which has a toString() method.
webinterface.d(110): function toString () does not match argument types 
(uint)

As a temporary solution I declared the following:
char[] toAString(int i) {
	return toString(i);
}
char[] realToString(real i) {
	return toString(i);
}

and used those instead, but IMHO the compiler should still look at 
global symbols if a local symbol matches the name but not the arguments.

By the way, the reason those have different names is because DMD gets 
confused if they're the same...

char[] toAString(int i) {
	return toString(i);
}
char[] toAString(real i) {
	return toString(i);
}
real mass;
toAString(mass);

webinterface.d(110): function toAString overloads char[](int i) and 
char[](real i) both match argument list for toAString

I'd think it would go for toAString(real) since the argument is actually 
a real, but it doesn't! It just refuses to compile, heh.

Also, something similar...

real mass;
int orbit;
real sunHU;
this.getHE=mass*sunHU*(1/(pow(pow(1.9,orbit),2)));
Doesn't work.

spacesim.d(206): function pow overloads real(real x,uint n) and 
real(real x,real y) both match argument list for pow

So I figured, hey, I'll just cast orbit to a uint and it should know 
what to do.

this.getHE=mass*sunHU*(1/(pow(pow(1.9,(uint)orbit),2)));

But it still doesn't work (and gives the same error message).

So I tried casting it to a real.
this.getHE=mass*sunHU*(1/(pow(pow(1.9,(real)orbit),2)));

That one worked (Go figure), but the thing is, I really wanted it to 
call the uint one, because if it's calling the real one, it's not 
checking for the special-cases that can be done faster (0, 1, and 2).

Oddly, the outer pow doesn't get confused. Its first parameter is still 
a real and the outer one is some form of int - but maybe it works 
because it's a constant. Hm.

Well, that's all for now.

-SL
Mar 24 2004
next sibling parent Carlos Santander B. <Carlos_member pathlink.com> writes:
Comments embedded.

In article <c3s7nd$2kvs$1 digitaldaemon.com>, SL says...

These are some weird error messages I've gotten that could probably make 
more sense if changed, and also a few things that could possibly use 
tweaking (and issues with calling overloaded functions, apparently):

'yearStr.length' is not an lvalue

Got that one from trying to do somearray.length+=1; (or -=, etc)
So I had to do somearray.length=somearray.length+1; instead, which is 
not too much of a hassle, but is weird. Also note that there was no 

make sense to someone who doesn't know what an lvalue is (AFAIK it's 
something that can be on the left hand side of an =, which 
somearray.length SHOULD be, I would think) or thinks it IS an lvalue and 
the compiler is wrong. So it's not exactly easy to track down and figure 
out (the first time you get it anyways, after that you know what to look 
for).


This is on purpose. You can't change the length of an array that way.
About the error messages, you're right. But I believe Walter is trying to make
improvements there.


 ...
Also, toString(someNumberTypeHere) doesn't work when trying to use it 
from a class which has a toString() method.
webinterface.d(110): function toString () does not match argument types 
(uint)

As a temporary solution I declared the following:
char[] toAString(int i) {
	return toString(i);
}
char[] realToString(real i) {
	return toString(i);
}

and used those instead, but IMHO the compiler should still look at 
global symbols if a local symbol matches the name but not the arguments.


Use .toString(someNumberTypeHere) instead (notice the dot).


...


-------------------
Carlos Santander B.
Mar 24 2004
prev sibling next sibling parent reply J Anderson <REMOVEanderson badmama.com.au> writes:
SL wrote:


 These are some weird error messages I've gotten that could probably 
 make more sense if changed, and also a few things that could possibly 
 use tweaking (and issues with calling overloaded functions, apparently):

 'yearStr.length' is not an lvalue

 Got that one from trying to do somearray.length+=1; (or -=, etc)



I believe, Walter's main reason against banning (++,--,+=,-=) is that 
it's inefficient to increment one value at a time (although the += could 
be used for more then once value :( ).  Generally when you adding one 
value you might as well use ~=.  It's also the same with pointers.  If 
you need to add a lot of elements it should be done outside the loop or 
in blocks as nessary.

-- 
-Anderson: http://badmama.com.au/~anderson/
Mar 24 2004
parent reply SL <shadowlord13 users.sourceforge.net> writes:
J Anderson wrote:

 I believe, Walter's main reason against banning (++,--,+=,-=) is that 
 it's inefficient to increment one value at a time (although the += could 
 be used for more then once value :( ).  Generally when you adding one 
 value you might as well use ~=.  It's also the same with pointers.  If 
 you need to add a lot of elements it should be done outside the loop or 
 in blocks as nessary.
 


If that was the goal, it didn't really stop me from doing it 
inefficiently. Heh. In any case, I wanted to prototype it fast, so I 
didn't bother with having a separate int numReports and resizing the 
array by large amounts only rarely, which is what I'd normally do.

I thought ~ and ~= only worked with strings? (This is an array of 
strings (char[][]) and I'm resizing the array, not individual strings)
Mar 24 2004
parent J Anderson <REMOVEanderson badmama.com.au> writes:
SL wrote:


 J Anderson wrote:


 I believe, Walter's main reason against banning (++,--,+=,-=) is that 
 it's inefficient to increment one value at a time (although the += 
 could be used for more then once value :( ).  Generally when you 
 adding one value you might as well use ~=.  It's also the same with 
 pointers.  If you need to add a lot of elements it should be done 
 outside the loop or in blocks as nessary.


 If that was the goal, it didn't really stop me from doing it 
 inefficiently. 


It does not stop you but It's kinda like a warning.  I think it mostly 
applies to ++ which only ever increments by one.


 Heh. In any case, I wanted to prototype it fast, so I didn't bother 
 with having a separate int numReports and resizing the array by large 
 amounts only rarely, which is what I'd normally do.

 I thought ~ and ~= only worked with strings? (This is an array of 
 strings (char[][]) and I'm resizing the array, not individual strings)


There is nothing different from char arrays to any other array, except 
that char arrays are treated as strings by convention.

-- 
-Anderson: http://badmama.com.au/~anderson/
Mar 24 2004
prev sibling next sibling parent J C Calvarese <jcc7 cox.net> writes:
SL wrote:

 These are some weird error messages I've gotten that could probably make 
 more sense if changed, and also a few things that could possibly use 
 tweaking (and issues with calling overloaded functions, apparently):
 
 'yearStr.length' is not an lvalue


I'm not a big fan of this error message either (maybe it should say 
"Can't '++' length"), but what really slowed me down was the lack of a 
line number. (That's why I posted an error report on it: 
http://www.digitalmars.com/drn-bin/wwwnews?D/25540.)

-- 
Justin
http://jcc_7.tripod.com/d/
Mar 24 2004
prev sibling parent Stewart Gordon <smjg_1998 yahoo.com> writes:
SL wrote:


 These are some weird error messages I've gotten that could probably make 
 more sense if changed, and also a few things that could possibly use 
 tweaking (and issues with calling overloaded functions, apparently):
 
 'yearStr.length' is not an lvalue
 
 Got that one from trying to do somearray.length+=1; (or -=, etc)
 So I had to do somearray.length=somearray.length+1; instead, which is 
 not too much of a hassle, but is weird. Also note that there was no 

 make sense to someone who doesn't know what an lvalue is (AFAIK it's 
 something that can be on the left hand side of an =, which 
 somearray.length SHOULD be, I would think)


<snip>

I think DMD has redefined it to mean something that can be on the LHS of 
a ++, -- or op=.  Of course, that's before you get to classes that may 
have none, some or all of them defined....


 spacesim.d(205): Array operations not implemented
 
 I got that one when I tried doing someString+someOtherString. I had 
 momentarily forgotten I was supposed to use ~, and it took me a few 
 seconds to figure out what the problem was, because the error message 
 looked like something totally different. A clearer message, such as "Use 
 the ~ operator to concatenate strings, not +" would help when 
 (inevitably) people try to use + with strings.


What if someone really is trying to do vector arithmetic on strings, 
e.g. when implementing a Vigenère cipher?


 Also, toString(someNumberTypeHere) doesn't work when trying to use it 
 from a class which has a toString() method.
 webinterface.d(110): function toString () does not match argument types 
 (uint)


You need to override the scope inference by either the fully qualified 
name (std.string.toString) or simply a dot prefix (.toString).

Presumably it assumes that you're trying to access a method within the 
class, but have misremembered or mistyped the argument list.

<snip>

 char[] toAString(int i) {
     return toString(i);
 }
 char[] toAString(real i) {
     return toString(i);
 }
 real mass;
 toAString(mass);
 
 webinterface.d(110): function toAString overloads char[](int i) and 
 char[](real i) both match argument list for toAString
 
 I'd think it would go for toAString(real) since the argument is actually 
 a real, but it doesn't! It just refuses to compile, heh.


You're right, there does seem to be a bug there.


 Also, something similar...
 
 real mass;
 int orbit;
 real sunHU;
 this.getHE=mass*sunHU*(1/(pow(pow(1.9,orbit),2)));
 Doesn't work.
 
 spacesim.d(206): function pow overloads real(real x,uint n) and 
 real(real x,real y) both match argument list for pow


That's in the spec:

"In D, function overloading is simple. It matches exactly, it matches 
with implicit conversions, or it does not match. If there is more than 
one match, it is an error."

Matches are (real, uint) and (real, real).  You call it by (double, 
uint).  Neither matches exactly, so it tries to match by implicit 
conversions.  But since both match, it fails.

<snip>

 So I tried casting it to a real.
 this.getHE=mass*sunHU*(1/(pow(pow(1.9,(real)orbit),2)));
 
 That one worked (Go figure), but the thing is, I really wanted it to 
 call the uint one, because if it's calling the real one, it's not 
 checking for the special-cases that can be done faster (0, 1, and 2).


	pow(1.9L, cast(uint) orbit)

IINM, the L creates a real literal.


 Oddly, the outer pow doesn't get confused. Its first parameter is still 
 a real and the outer one is some form of int - but maybe it works 
 because it's a constant. Hm.


Good question.  Maybe there's a bug here, or maybe there's an 
undocumented feature meaning that an int literal can be treated as a 
uint if it disambiguates.

Stewart.

-- 
My e-mail is valid but not my primary mailbox, aside from its being the 
unfortunate victim of intensive mail-bombing at the moment.  Please keep 
replies on the 'group where everyone may benefit.
Mar 26 2004