Type detection: Difference between revisions

=={{header|Pascal}}==

===Dispatch by variant record===

Pascal has a plethora of dialects, and so I have tried to be as close to ''Algorithms + Data Structures = Programs'' (Wirth) style as I could figure out how, when using the Free Pascal Compiler.

<lang pascal>program type_detection_demo (input, output);

type

source_t = record case kind : (builtintext, filetext) of

builtintext : (i : integer);

filetext : (f : file of char);

end;

var

source : source_t;

input : file of char;

c : char;

procedure print_text (var source : source_t);

begin

case source.kind of

builtintext : case source.i of

1 : writeln ('This is text 1.');

2 : writeln ('This is text 2.')

end;

filetext : while not eof (source.f) do

begin

read (source.f, c);

write (c)

end

end

end;

begin

assign (input, 'type_detection-pascal.pas');

reset (input);

with source do

begin

kind := builtintext;

i := 1;

print_text (source);

i := 2;

print_text (source);

kind := filetext;

f := input;

print_text (source)

end

end.</lang>

{{out}}

$ fpc -Miso type_detection-pascal.pas && ./type_detection-pascal

<pre>This is text 1.

This is text 2.

program type_detection_demo (input, output);

type

source_t = record case kind : (builtintext, filetext) of

builtintext : (i : integer);

filetext : (f : file of char);

end;

var

source : source_t;

input : file of char;

c : char;

procedure print_text (var source : source_t);

begin

case source.kind of

builtintext : case source.i of

1 : writeln ('This is text 1.');

2 : writeln ('This is text 2.')

end;

filetext : while not eof (source.f) do

begin

read (source.f, c);

write (c)

end

end

end;

begin

assign (input, 'type_detection-pascal.pas');

reset (input);

with source do

begin

kind := builtintext;

i := 1;

print_text (source);

i := 2;

print_text (source);

kind := filetext;

f := input;

print_text (source)

end

end.</pre>