Hi again!

I (Peter Gerwinski) wrote:

This is an example entry for how I think our joined effort to complete the GPC reference could work. The section I am posting is already in existence (`abs'):

[...]

@unnumberedsubsec Description

Returns the absolute value of the argument:

@smallexample Function abs ( x: @var{some type} ): @var{some type};

begin (* abs *) if x < 0 then abs:= -x else abs:= x; end (* abs *); @end smallexample

Whoever wrote this ;-) forgot to think about complex values. A suggested correction follows below.

begin writeln ( abs ( 42 ) ); (* 42 *); writeln ( abs ( -42 ) ); (* 42 *); writeln ( abs ( -12.1 : 0 : 1 ) ); (* 12.1 *); i1:= cmplx ( 1, 1 ); (* 1 + i *) writeln ( abs ( i1 ) : 0 : 10 ); (* yields 1.4142135624, i.e. sqrt ( 2 ) *) end.

Maybe the comments should be in one column?

@c ----------------------------------------------------------------------------

@node abs @unnumberedsec abs @cindex abs

@unnumberedsubsec Syntax

@smallexample Function abs ( i: @var{integer type} ): @var{integer type}; @end smallexample or @smallexample Function abs ( x: @var{real type} ): @var{real type}; @end smallexample or @smallexample Function abs ( z: @var{complex type} ): @var{real type}; @end smallexample

@unnumberedsubsec Description

Returns the absolute value of the argument. For integer or real values of @samp{x}, the definition is

@smallexample Function abs ( x: @var{integer or real type} ): @var{integer or real type};

begin (* abs *) if x < 0 then abs:= -x else abs:= x; end (* abs *); @end smallexample

whereas for complex values it is

@smallexample Function abs ( x: Complex ): Complex;

begin (* abs *) abs:= sqrt ( x * conjugate ( x ) ); end (* abs *); @end smallexample

@unnumberedsubsec Standards

The function @samp{abs} is defined in ISO-7185 Standard Pascal; its application to complex values is defined in ISO-10206 Extended Pascal.

@unnumberedsubsec Example

@smallexample Program TestAbs;

Var i1: Complex;

begin writeln ( abs ( 42 ) ); (* 42 *); writeln ( abs ( -42 ) ); (* 42 *); writeln ( abs ( -12.1 : 0 : 1 ) ); (* 12.1 *); i1:= cmplx ( 1, 1 ); (* 1 + i *) writeln ( abs ( i1 ) : 0 : 3 ); (* 1.414, i.e. sqrt ( 2 ) *) end. @end smallexample

@unnumberedsubsec See also

@ref{sqr}.

@c ----------------------------------------------------------------------------

If you follow-up to this mail and modify the section, please include a complete copy without leading "> " or such in order to make it easier for me to integrate the modified copy into `reference.texi'.

I did so. ;-)

Okay - now it's your turn! (-:

Peter

According to Maurice Lombardi:

...

...

writeln ( abs ( -12.1 : 0 : 1 ) );  (* 12.1 *);

                       ^^^^^^^^^^^
                            I think, something is goin wrong...

No no, at least in BP, the actual length is adjusted upwards to contain what needs to be written if the specified length is too short. [...]

No, that was not the issue: Carefully watch the nesting of the parentheses ... ;-)

Peter