Pascal Viandier wrote:

During some tests I ran with gpc 2050331 to evaluate the gap between SUN and GNU Pascal, I discovered that the function TRIM() is broken when it is passed a packed array of char.

The small program bellow shows incorrect result:

PROGRAM Trim; VAR St : PACKED ARRAY [1..20] OF CHAR; I : INTEGER; BEGIN WriteLn('Before assignment:'); FOR I := 1 TO 20 DO WriteLn('St[', i:2,']=', Ord(St[i])); { This shows a series of 0 } WriteLn('After assignment:'); St := 'The String'; FOR I := 1 TO 20 DO WriteLn('St[', i:2,']=', Ord(St[i])); { This shows the string padded with blanks (CHR(32)} St := Trim(St); WriteLn('After Trim:'); FOR I := 1 TO 20 DO WriteLn('St[', i:2,']=', Ord(St[i])); { ***This shows the string exactly AS BEFORE! } END.

Am I right when I think the function TRIM should replace the blanks with some CHR(0)?

Nope. Fixed strings (i.e., packed arrays of char) are blank-padded on assignments (EP, 6.4.6 last paragraph). This implicit operation effectively undoes the effect of `Trim'.

Bottom line: There's no direct way to store strings with and without trailing spaces in fixed-strings (as strings with trailing spaces as some kind of "un-strings" in standard Pascal, one thing I dislike most about it). The only way is to store the length in a separate variable (which means reimplementing many built-in string operations), or use EP strings (`String (20)') which store their length and are not automatically blank padded.

BTW, Chr (0) has no significance as a string terminator in Pascal. (GPC adds it when "converting" to a CString, but that's about it, and this won't help you here.)

Frank

Hi,

During some tests I ran with gpc 2050331 to evaluate the gap between SUN and GNU Pascal, I discovered that the function TRIM() is broken when it is passed a packed array of char.

The small program bellow shows incorrect result:

PROGRAM Trim; VAR St : PACKED ARRAY [1..20] OF CHAR; I : INTEGER; BEGIN WriteLn('Before assignment:'); FOR I := 1 TO 20 DO WriteLn('St[', i:2,']=', Ord(St[i])); { This shows a series of 0 }

This writes any garbage contained in St (since St is uninitialized)

WriteLn('After assignment:');
St := 'The String';
FOR I := 1 TO 20 DO WriteLn('St[', i:2,']=', Ord(St[i])); { This shows

the string padded with blanks (CHR(32)} St := Trim(St);

^^^^^^^^^^^^^^^ This is a no-op

WriteLn('After Trim:');
FOR I := 1 TO 20 DO WriteLn('St[', i:2,']=', Ord(St[i])); { ***This

shows the string exactly AS BEFORE! }

As expected.

END.

Am I right when I think the function TRIM should replace the blanks with some CHR(0)?

No, TRIM makes _shorter_ string remowing blanks at the end. Assignment pads the value with blanks to fill whole St. You can see the difference if you have:

program tstrim(Output); Var Sv : String(20); St : packed array [1..20] of char; begin St := 'The String'; writeln('->', St, '<-'); Sv := St; writeln('->', Sv, '<-'); Sv := TRIM(St); writeln('->', Sv, '<-'); St := Sv; writeln('->', St, '<-'); end .

Blank padding on assignment is required by ISO standards.