Re: [Seed7-users] Pointer to function as argument

[Thomas M. <tho...@gm...>]

In the example below the arguments 'a' and 'b' are read at runtime:
 
-------------------- begin l_skov.sd7 --------------------
$ include "seed7_05.s7i";

const proc: tester (in var integer: a, in var integer: b, ref func integer: fun) is func
  begin
    writeln("Value of fun: " <& fun);
    writeln("end");
    writeln("inside: a = " <& a);
    writeln("inside: b = " <& b);
  end func;

const proc: main is func
  local
    var integer: a is 0;
    var integer: b is 0;
  begin
    write("a? ");
    readln(a);
    write("b? ");
    readln(b);
    tester(a, b, a+b);
  end func;
-------------------- end l_skov.sd7 --------------------

The function 'tester' can also work without the parameters 'a' and 'b':

-------------------- begin l_skov2.sd7 --------------------
$ include "seed7_05.s7i";

const proc: tester (ref func integer: fun) is func
  begin
    writeln("Value of fun: " <& fun);
  end func;

const proc: main is func
  local
    var integer: a is 0;
    var integer: b is 0;
  begin
    write("a? ");
    readln(a);
    write("b? ");
    readln(b);
    tester(a+b);
    tester(a*b);
  end func;
-------------------- end l_skov2.sd7 --------------------

Regarding your 2nd question:
You can write
    boolean parse "TRUE"
because the syntax of the 'parse' operator is defined in the file syntax.s7i with:
    $ syntax expr: .().parse.()                  is <-   1;

The syntax of function calls like
    writeln("something")
is not defined explicit (in e.g. syntax.s7i).
Generally the syntax of all function calls
    function_name(parameter1, parameter2)
is hard coded. The hard coded syntax for function calls
requires parentheses around the parameters.

If there is a syntax definition then parentheses can be omitted.
E.g.: The 'not' operator is defined in syntax.s7i with:
    $ syntax expr: .not.()                       is <-  13;
This allows you to write
    not some_expression
without parentheses.


Regards,
Thomas Mertes

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