Bug or Not? Taking STRING of a string whilst making leading zeros
01-29-2018, 04:41 PM (This post was last modified: 01-29-2018 07:11 PM by StephenG1CMZ.)
Post: #1
 StephenG1CMZ Senior Member Posts: 979 Joined: May 2015
Bug or Not? Taking STRING of a string whilst making leading zeros
I discovered that if there is an unneccessary call to STRING the leading 0 doesnt appear.
Why aren't "9" and STRING("9") both of length 1, yielding 1 leading zero in the example code?
Code:
       ZEROS(NN)  //LEADING ZEROS  BEGIN   //MSGBOX(NN);   IF NN>0 THEN    RETURN "0"+ZEROS(NN-1);   END;   RETURN "";   END;       EXPORT ReDIGITS (ALT )  BEGIN   //LOCAL NDIGITS:=2;   LOCAL STR:="";   LOCAL ST:="";//STRINGVERSION    //CAS("temporary:=iquo((1*10^NDIGITS),2)");    //ST:=CAS("string(temporary)");    ST:="9";    //The string version asks for leading zeros I hoped    //but no...pad it manually     //STR:=CAS(format(ST,"s"+NDIGITS));    IF ALT THEN //EXPECTED     STR:=ZEROS(2-DIM((ST)));    ELSE    //UNEXPECTED     STR:=ZEROS(2-DIM(STRING(ST)));    END;    ST:=MID(STR+ST,TransientLEN+1);    MSGBOX(STR);    MSGBOX(ST);   END;   EXPORT STBUG()  BEGIN  END;
Try with Alt 1 and Alt 0 to see the expected and erroneous output.

Is there a better way to get leading zeros in a string?

Stephen Lewkowicz (G1CMZ)
https://my.numworks.com/python/steveg1cmz
01-29-2018, 05:21 PM
Post: #2
 Carlos295pz Senior Member Posts: 365 Joined: Sep 2015
RE: Bug: Taking STRING of a string whilst making leading zeros
Ans → 9
STRING(Ans) → "9"
STRING(Ans) → ""9""
STRING(Ans) → """"9""""
STRING(Ans) → """"""""9""""""""

Viga C | TD | FB
01-30-2018, 11:38 AM
Post: #3
 Didier Lachieze Senior Member Posts: 1,578 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
(01-29-2018 04:41 PM)StephenG1CMZ Wrote:  Why aren't "9" and STRING("9") both of length 1, yielding 1 leading zero in the example code?
"9" is a string of length 1, but STRING("9") is a string of length 3: '9' plus 2 double quote characters.

(01-29-2018 04:41 PM)StephenG1CMZ Wrote:  Is there a better way to get leading zeros in a string?
A simple way to get a string with N zeros: tail(STRING(10^N)), or if you prefer not to use a CAS function: MID(STRING(10^N),2,N).
It works for N>=0, returning "" for N=0.
01-30-2018, 12:53 PM (This post was last modified: 01-30-2018 02:58 PM by toml_12953.)
Post: #4
 toml_12953 Senior Member Posts: 2,039 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
(01-29-2018 04:41 PM)StephenG1CMZ Wrote:  Is there a better way to get leading zeros in a string?

If the number is N and length you want is X, I use:

Code:
RIGHT(MID(STRING(10^X,1),2)+N,X)

Thanks to Joe's post, I changed the STRING function to include the format type.

Tom L
Cui bono?
01-30-2018, 02:28 PM
Post: #5
 Joe Horn Senior Member Posts: 1,967 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
Warning #1: The output of STRING(X) depends on the current Number Format in Home Settings. For example, STRING(456) in Fixed 2 mode returns "456.00" which might not be what you want. To insure that whole numbers always get turned into strings without decimal places, use the optional second argument to specify the desired format regardless of the current setting. STRING(456,1) --> "456" (the 1 here means "use Standard number format").

Warning #2: In CAS programs, be sure to use the newer, smarter function STRING(), not its older, dumber sibling string(). Thankfully, Home always uses STRING().

<0|ɸ|0>
-Joe-
01-30-2018, 03:00 PM
Post: #6
 Didier Lachieze Senior Member Posts: 1,578 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
(01-30-2018 02:28 PM)Joe Horn Wrote:  Warning #1: The output of STRING(X) depends on the current Number Format in Home Settings.

Good Point ! I always forget it as I'm almost always in Standard number format.
01-30-2018, 03:25 PM
Post: #7
 toml_12953 Senior Member Posts: 2,039 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
(01-30-2018 03:00 PM)Didier Lachieze Wrote:
(01-30-2018 02:28 PM)Joe Horn Wrote:  Warning #1: The output of STRING(X) depends on the current Number Format in Home Settings.

Good Point ! I always forget it as I'm almost always in Standard number format.

Moi aussi. (Me too™)

Tom L
Cui bono?
01-30-2018, 07:58 PM (This post was last modified: 01-30-2018 08:00 PM by StephenG1CMZ.)
Post: #8
 StephenG1CMZ Senior Member Posts: 979 Joined: May 2015
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
Thanks for those tips - I was assuming STRING was cleverly turning whatever into a string and could leave "9" unchanged.
So far I have this for producing leading zeros (based on the above but handling 0 zeros):
Code:
  EXPORT NZEROS(NZ)  //ONLY WORKS FOR NZ<12  BEGIN   RETURN IFTE(NZ>0,MID(STRING(10^NZ),2),"");  END;
It only works with less than 12 zeros...
I am surprised there is no built-in for this.

Stephen Lewkowicz (G1CMZ)
https://my.numworks.com/python/steveg1cmz
01-30-2018, 08:16 PM (This post was last modified: 01-30-2018 08:17 PM by Didier Lachieze.)
Post: #9
 Didier Lachieze Senior Member Posts: 1,578 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
Here is a version without the limitation of NZ<12:
Code:
EXPORT NZEROS(NZ) BEGIN  RETURN CAS("tail(string(10^NZ))"); END;

(01-30-2018 02:28 PM)Joe Horn Wrote:  Warning #2: In CAS programs, be sure to use the newer, smarter function STRING(), not its older, dumber sibling string(). Thankfully, Home always uses STRING().
What's the difference between the two functions?
01-30-2018, 08:17 PM
Post: #10
 Han Senior Member Posts: 1,882 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
Either make a "constant" string of more-than-enough 0's and append it to the front of your number, or create a function that will produce such a string by repeatedly adding a small string of zero's to itself and then append this to the front. Then simply "cut" the desired length using MID().

Graph 3D | QPI | SolveSys
01-30-2018, 08:48 PM
Post: #11
 StephenG1CMZ Senior Member Posts: 979 Joined: May 2015
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
(01-30-2018 08:16 PM)Didier Lachieze Wrote:  Here is a version without the limitation of NZ<12:
Code:
EXPORT NZEROS(NZ) BEGIN  RETURN CAS("tail(string(10^NZ))"); END;

(01-30-2018 02:28 PM)Joe Horn Wrote:  Warning #2: In CAS programs, be sure to use the newer, smarter function STRING(), not its older, dumber sibling string(). Thankfully, Home always uses STRING().
What's the difference between the two functions?

Neat solution.
I am surprised that the obvious recursive solution is faster (and can recurse up to at least 1000 digits):
Code:
 EXPORT ZEROS(NN)  BEGIN   IF NN>0 THEN    RETURN "0"+ZEROS(NN-1);   END;   RETURN "";   END;
I had expected that the recursive solution would be worse.

Stephen Lewkowicz (G1CMZ)
https://my.numworks.com/python/steveg1cmz
01-30-2018, 09:19 PM
Post: #12
 toml_12953 Senior Member Posts: 2,039 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
(01-30-2018 08:17 PM)Han Wrote:  Either make a "constant" string of more-than-enough 0's and append it to the front of your number, or create a function that will produce such a string by repeatedly adding a small string of zero's to itself and then append this to the front. Then simply "cut" the desired length using MID().
Yup, that what the line I posted does. It works and is pretty easy to understand.

Tom L
Cui bono?
01-30-2018, 09:36 PM (This post was last modified: 01-30-2018 09:37 PM by Carlos295pz.)
Post: #13
 Carlos295pz Senior Member Posts: 365 Joined: Sep 2015
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
The recursive function may look like this:
Code:
EXPORT ZEROS(NZ) BEGIN    IFTE(NN,"0"+ZEROS(NZ-1),"") END;

Speed may not be important for that code, but it may be better to use ITERATE instead of tail.
Code:
EXPORT ZEROS(NZ) BEGIN    ITERATE(X+"0",X,"0",NZ) END;

Viga C | TD | FB
01-31-2018, 03:05 AM
Post: #14
 Jacob Wall Member Posts: 161 Joined: Dec 2013
RE: Bug or Not? Taking STRING of a string whilst making leading zeros
Some interesting solutions I might not have thought of myself.

Here are two functions I've been using to left- or right-justify a string. Arguments are a string to be processed, the desired length of the resulting string, and the filler character, could be anything but probably 0 or space most common. T

Code:
StrLJust(str,len,spacer) BEGIN   LOCAL j,strdim:=DIM(str);   IF len>strdim THEN     FOR j FROM strdim TO len-1 DO       str:=str+spacer;     END;   END;   RETURN(str); END; StrRJust(str,len,spacer) BEGIN   LOCAL j,strdim:=DIM(str);   IF len>strdim THEN     FOR j FROM strdim TO len-1 DO       str:=spacer+str;     END;   END;   RETURN(str); END;

But looking at the ITERATE command, this can definitely be made more compact:
Code:
StrLJust(str,len,spacer) BEGIN   RETURN(IFTE(DIM(str)<len,str+ITERATE(str+spacer,str,spacer,len-DIM(str)-1),str); END; StrLRJust(str,len,spacer) BEGIN   RETURN(IFTE(DIM(str)<len,ITERATE(str+spacer,str,spacer,len-DIM(str)-1)+str,str); END;

Thanks Carlos! Have you made benchmark comparisons between FOR loop and ITERATE? Would be curious if one is faster than the other.
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