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Create your own text control codes

From Rosetta Code
Create your own text control codes is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

A control code is a text character or sequence of characters with a special meaning that, rather than print a text character to the terminal or screen, instructs the computer to do something text-related. Examples include:

  • NUL (ASCII 0) = The null terminator. Most programming languages silently place this at the end of a string so that the print function knows when to stop.
  • \n (New Line) = This tells the print function to start a new line. Older computers don't have this, rather they use an ASCII 13 (carriage return) followed by an ASCII 10 (line feed).
  • \ (Escape Character) = Any control code placed directly after the escape character loses is special meaning and is printed as-is.
  • %d = Insert a base 10 numeral into the string. The value is loaded from a variable specified after the string, separated by commas.

The C code below shows the %d control code in action:

int foo = 1;
int bar = 2;
int baz = foo + bar;
printf("%d plus %d is: %d",foo,bar,baz); //outputs "1 plus 2 is: 3"


Task

Add a new control code to your language's standard print function, which does some sort of text related task that is not already built into the language. Have the standard print function print a string that uses that code, and display the output. What the control code actually does is up to you, but some examples include:

  • Changing the color of the text
  • Starting a new line at a custom location, without padding the string with blank spaces


If the language allows, try to make something entirely new that isn't just a macro of existing control codes combined to produce a trivial result (e.g. \n\n\n\n for four new lines would be trivial)

If your language doesn't allow you to modify the standard print function, note it. (This is a draft task for now because I don't know if anything other than assembly can do this.)

8086 Assembly[edit]

In languages where you have to write your own print function, this task is relatively straightforward. MS-DOS has a "PrintString" function built-in, but this example will use a custom one with its own control codes. Currently this print function supports two types of control codes beyond the standard ones: a set of control codes that change the text color, and one that starts a new line with a specified number of spaces.

(Generally speaking, the implementation below isn't the best way to do it for compatibility reasons, since you end up sacrificing the ability to print certain characters. It's usually better to have one escape character and then the character after it becomes the control code. That way you only sacrifice one character instead of dozens. And technically you don't even lose the escape character since it can always escape itself by doubling it up.)

The routine below is called repeatedly by a routine named PrintString_Color until the null terminator is read.

PrintChar_Color:		;Print AL to screen
push dx
push ax
mov dx,8F80h
call CompareRange8 ;sets carry if 80h <= al <= 8Fh, clears carry otherwise
jc isColorCode
cmp al,90h
jne skipCCR_Color
call CustomCarriageReturn ;prints new line, then moves cursor a variable amount of spaces forward.
;this variable is set prior to printing a string that needs it.
jmp done_PrintChar_Color
skipCCR_Color:
mov ah,0Eh
int 10h ;prints character AL to screen, with the ink color stored in BL.
jmp done_PrintChar_Color
isColorCode:
and al,01111111b ;clear bit 7 to convert to VGA colors.
mov bl,al ;text from this point forward will use this color.
done_printChar_Color:
pop ax
pop dx
ret


Julia[edit]

The example below extends the Base show function, as used to stringify printed output, to allow formatting of larger numbers with commas and to print negative integers with parentheses.

using Formatting
import Base.show
 
Base.show(io::IO, x::Float64) = print(io, format(x, commas=true))
Base.show(io::IO, x::Int) = print(io, format(x, commas=true, parens=true))
 
println("15.1 + 31415926.5 = $(15.1 + 31415926.5)")
println("10000000000 / -3 = $(10000000000 / -3)")
println("2345 * 76 = $(2345 * 76), 2345 * -9876 = $(2345 * -9876)")
 
Output:
15.1 + 31415926.5 = 31,415,941.6
10000000000 / -3 = -3,333,333,333.333333
2345 * 76 =  178,220 , 2345 * -9876 = (23,159,220)


Phix[edit]

The printf() function is implemented in fairly standard Phix hll code in builtins\VM\pprntfN.e
Recent-ish additions along the lines of the task description include:
%q, %Q (print with quotes)
%v, %V (apply sprint internally)
%a, %A (print in bases 2..62)
%[i]specifier (print i'th arg here)
%=specifier (centre, with odd padding as eg 3:4)
%|specifier (centre, with odd padding as eg 4:3)
Just as an example, so we can have some actual code here, but omitting the setup of "centre" from the format string, the latter two were mainly implemented as follows:

                    elsif centre then
                        integer mh = floor(minfieldwidth/2)
                        if centre=1 then    -- '=', split 3:4
                            r1 = repeat(' ',mh)&r1&repeat(' ',minfieldwidth-mh)
                        else                -- '|', split 4:3
                            r1 = repeat(' ',minfieldwidth-mh)&r1&repeat(' ',mh)
                        end if

At the same time, similar changes were made to the version of printf() defined in pwa/p2js.js:

                    let padlen = parseInt(size,10)-res.length;
let half = Math.floor(padlen/2);
case '=': res = pad.repeat(half) + res + pad.repeat(padlen-half); break;
case '|': res = pad.repeat(padlen-half) + res + pad.repeat(half); break;

PL/M[edit]

PL/M doesn't have a standard printf function or indeed, a standard library. This sample implements a PRINTF procedure somewhat like the standard C library routine.

Although CP/M uses ASCII, Kildall's original 8080 PL/M compiler only supports a limited character set for the program's source. In particular the compiler doesn't like lowercase letters, % or \. PL/M also requires procedures to be called with the same number of parameters they were defined with. The PRINTF defined here has the format string plus seven parameters, if fewer parameters are required, additional dummy parameters must be supplied
As % and lowercase are not available, the format frames are preceeded by / and must be in uppercase.
The following are supported:

/S       -> print a string
/LS      -> print a string in lowercase
/C       -> print a single character
/LC      -> print a single character in lowercase
/D or /I -> print a signed integer in decimal
/U       -> print an unsigned integer in decimal
/H or /X -> print an unsigned integer in hexadecimal
/O       -> print an unsigned integer in octal
/N       -> print a newline
/anything-else
         -> print the anything-else character, e.g. /$ prints a $ without terminating the format

The additional options such as field width available in C's printf are not allowed in this PRINTF.

Note that under CP/M, strings are terminated by $, not a nul character, hence the need for /$.
The original 8080 PL/M compiler also only supports unsigned 8 and 16 bit values. If a number must be treated as signed, the values 65535 downto 32768 represent -1 downto -32768, hence the somewhat cryptic handling of the D and I frames.

100H: /* FORMATTED OUTPUT */
 
/* CP/M BDOS SYSTEM CALL */
BDOS: PROCEDURE( FN, ARG ); DECLARE FN BYTE, ARG ADDRESS; GOTO 5;END;
/* CONSOLE OUTPUT ROUTINES */
PR$CHAR: PROCEDURE( C ); DECLARE C BYTE; CALL BDOS( 2, C ); END;
PR$STRING: PROCEDURE( S ); DECLARE S ADDRESS; CALL BDOS( 9, S ); END;
PR$NL: PROCEDURE; CALL PR$STRING( .( 0DH, 0AH, '$' ) ); END;
PR$NUMBER: PROCEDURE( N );
DECLARE N ADDRESS;
DECLARE V ADDRESS, N$STR( 6 ) BYTE INITIAL( '.....$' ), W BYTE;
N$STR( W := LAST( N$STR ) - 1 ) = '0' + ( ( V := N ) MOD 10 );
DO WHILE( ( V := V / 10 ) > 0 );
N$STR( W := W - 1 ) = '0' + ( V MOD 10 );
END;
CALL PR$STRING( .N$STR( W ) );
END PR$NUMBER;
PR$OCTAL: PROCEDURE( N );
DECLARE N ADDRESS;
DECLARE V ADDRESS, N$STR( 7 ) BYTE INITIAL( '......$' ), W BYTE;
DO W = 0 TO LAST( N$STR ) - 2; N$STR( W ) = '0'; END;
N$STR( W := LAST( N$STR ) - 1 ) = '0' + ( ( V := N ) AND 7 );
DO WHILE( ( V := SHR( V, 3 ) ) > 0 );
N$STR( W := W - 1 ) = '0' + ( V AND 7 );
END;
CALL PR$STRING( .N$STR( W ) );
END PR$OCTAL;
 
/* FORMATTED PRINT ROUTINE - VAGUELY LIKE THE C ROUTINE */
PRINTF: PROCEDURE( FMT, A, B, C, D, E, F, G );
DECLARE ( FMT, A, B, C, D, E, F, G ) ADDRESS;
 
PR$HEX: PROCEDURE( B ); /* PRINTS B AS A 2 DIGIT HEX NUMBER */
DECLARE B BYTE;
DECLARE D BYTE;
IF ( D := SHR( B, 4 ) ) > 9 THEN CALL PR$CHAR( ( D - 10 ) + 'A' );
ELSE CALL PR$CHAR( D + '0' );
IF ( D := B AND 0FH ) > 9 THEN CALL PR$CHAR( ( D - 10 ) + 'A' );
ELSE CALL PR$CHAR( D + '0' );
END PR$HEX ;
/* RETURNS A CONVERTED TO LOWERCASE, IF NECESSARY */
TO$LOWER: PROCEDURE( A )BYTE;
DECLARE A BYTE;
IF A >= 'A' AND A <= 'Z' THEN RETURN ( A + 32 ); ELSE RETURN A;
END TO$LOWER;
 
DECLARE FRAME LITERALLY '''/''';
DECLARE P ( 7 )ADDRESS;
DECLARE FPTR ADDRESS;
DECLARE ( PPOS, FCH BASED FPTR, IN$LOWERCASE ) BYTE;
P( 0 ) = A; P( 1 ) = B; P( 2 ) = C; P( 3 ) = D;
P( 4 ) = E; P( 5 ) = F; P( 6 ) = G;
PPOS = 0;
FPTR = FMT;
DO WHILE( FCH <> '$' );
IF FCH <> FRAME THEN DO; /* NOT A FORMAT FRAME */
CALL PR$CHAR( FCH );
END;
ELSE DO; /* IS A FORMAT FRAME */
FPTR = FPTR + 1;
IF ( IN$LOWERCASE := FCH = 'L' ) THEN FPTR = FPTR + 1;
IF FCH = 'C' OR FCH = 'S' THEN DO;
/* CHARACTER OR STRING OPTIONALLY CONVERTED TO LOWER CASE */
IF FCH = 'C' THEN DO; /* CHARACTER */
IF IN$LOWERCASE THEN CALL PR$CHAR( TO$LOWER( P( PPOS ) ) );
ELSE CALL PR$CHAR( P( PPOS ) );
END;
ELSE IF NOT IN$LOWERCASE THEN DO; /* STRING AS-IS */
CALL PR$STRING( P( PPOS ) );
END;
ELSE DO; /* LOWERCASE STRING */
DECLARE SPTR ADDRESS;
DECLARE SCH BASED SPTR BYTE;
SPTR = P( PPOS );
DO WHILE( SCH <> '$' );
CALL PR$CHAR( TO$LOWER( SCH ) );
SPTR = SPTR + 1;
END;
END;
PPOS = PPOS + 1;
END;
ELSE IF FCH = 'I' OR FCH = 'D' OR FCH = 'U' THEN DO;
/* SIGNED OR UNSIGNED DECIMAL INTEGER */
DECLARE V ADDRESS;
V = P( PPOS );
IF FCH <> 'U' AND V > 32767 THEN DO;
/* THE NUMBER IS NEGATIVE AND MUST BE PRINTED AS SIGNED */
CALL PR$CHAR( '-' );
V = - V;
END;
CALL PR$NUMBER( V );
PPOS = PPOS + 1;
END;
ELSE IF FCH = 'H' OR FCH = 'X' THEN DO;
/* UNSIGNED INTEGER IN HEX */
DECLARE V ADDRESS;
V = P( PPOS );
CALL PR$CHAR( '$' );
CALL PR$HEX( HIGH( V ) );
CALL PR$HEX( LOW( V ) );
PPOS = PPOS + 1;
END;
ELSE IF FCH = 'O' THEN DO; /* UNSIGNED OCTAL INTEGER */
CALL PR$OCTAL( P( PPOS ) );
PPOS = PPOS + 1;
END;
ELSE IF FCH = 'N' THEN DO; /* NEWLINE */
CALL PR$NL;
END;
ELSE DO; /* ANYTHING ELSE - JUST PRINT IT */
CALL PR$CHAR( FCH );
END /* IF VARIOUS FRAMES;; */ ;
END /* IF FCH <> FRAME;; */ ;
FPTR = FPTR + 1;
END /* WHILE FCH <> '$' */ ;
END PRINTF ;
 
/* TEST PRINTF */
DECLARE ( P3, P4, P5, P6, P7 ) ADDRESS;
P3 = 301; P4, P5, P6 = 0;
P3 = - P3; P4 = P4 - 1; P5 = P5 - 2; P6 = P6 - 3; P7 = 65535;
CALL PRINTF( .'HELLO, /S/C /I/$ /D /U /X./N(END)/O/N$'
, .'WORLD$', 33, P3, P4, P5, P6, P7
);
CALL PRINTF( .'H/LC/LC/LC/LC, W/LS/C$'
, 'E', 'L', 'L', 'O', .'ORLD$', 33, 0
);
EOF
Output:
HELLO, WORLD! -301$ -1 65534 $FFFD.
(END)177777
Hello, World!

Raku[edit]

This, in general would be a bad idea. It isn't smart to add a lot of overhead to core functions, especially for so little gain. That being said, something being a bad idea never stopped us before.

printf already has so many directives, most of the good mnemonics are already taken. Add a "commas" directive as %y and an "invert" directive as %z.

Some languages already have a commas directive as that one is actually useful. I doubt if any language has an "invert" directive.

This is really basic and sketchy. It only modifies printf, not sprintf, so probably isn't terribly useful as is... but it satisfies the task requirements. It actually does add new, non-standard directives to the core printf function, not just implement a separate formatting function to pre-format a string which is then passed to the printing function.

use Lingua::EN::Numbers;
use Acme::Text::UpsideDown;
 
sub printf (Str $format is copy, *@vars is copy) {
my @directives = $format.comb(/ <?after <-[%]>|^> '%' <[ +0#-]>* <alpha>/);
for ^@directives {
if @directives[$_] eq '%y' {
$format.=subst('%y', '%s');
@vars[$_].=&comma;
} elsif @directives[$_] eq '%z' {
$format.=subst('%z', '%s');
@vars[$_].=&upsidedown;
}
}
&CORE::printf($format, @vars)
}
 
printf "Integer %d with commas: %y\nSpelled out: %s\nInverted: %z\n",
12345, 12345, 12345.&cardinal, 12345.&cardinal;
Output:
Integer 12345 with commas: 12,345
Spelled out: twelve thousand, three hundred forty-five
Inverted: ǝʌᴉɟ-ʎʇɹoɟ pǝɹpunɥ ǝǝɹɥʇ ‘puɐsnoɥʇ ǝʌꞁǝʍʇ

Wren[edit]

Wren's standard print statement, System.print (or System.write without a terminating new line), has no formatting capabilities whatsoever though it does support string interpolation. It cannot be changed without forking Wren itself.

When doing RC tasks, I often use methods in my own Wren-fmt module which does most of what C's printf statement does and other things besides. Although I could add anything I like to that, it's already more than 800 lines long and so I don't think it would be appropriate to patch it for the purposes of this task.

What I've done instead is to create a special class called Sgr (Select graphic rendition) which adds special effects when printing text to terminals which support ANSI escape sequences. The effects supported are: color, bold, faint, italic, underline, wink, strike and overline each of which is represented by a method consisting of its initial letter.

When these methods complete, they restore the terminal attributes to what they were before. System.print can now interpolate these method calls.

Although it would be possible to abbreviate the color arguments passed to Sgr.c, I haven't done so because I didn't think it would be very user friendly.

class Sgr {
// capitalize the initial letter for bright colors
static init_() {
__cm = { "black": 30, "red" : 31, "green": 32, "yellow": 33,
"blue" : 34, "magenta": 35, "cyan" : 36, "white" : 37,
"Black": 90, "Red" : 91, "Green": 92, "Yellow": 93,
"Blue" : 94, "Magenta": 95, "Cyan" : 96, "White" : 97,
"gray" : 90, "Gray" : 90
}
}
 
static c(fore, back, text) { // colorize
if (!__cm) init_()
var fcn = __cm[fore]
if (!fcn) Fiber.abort("Invalid foreground color.")
var bcn = __cm[back]
if (!bcn) Fiber.abort("Invalid background color.")
if (!(text is String)) text = text.toString
var reset = "\e[39;49m"
return "\e[%(fcn);%(bcn+10)m%(text)%(reset)"
}
 
 
static b(text) { "\e[1m%(text)\e[22m" } // bold
 
static f(text) { "\e[2m%(text)\e[22m" } // faint
 
static i(text) { "\e[3m%(text)\e[23m" } // italic
 
static u(text) { "\e[4m%(text)\e[24m" } // underline
 
static w(text) { "\e[5m%(text)\e[25m" } // wink (or blink)
 
static r(text) { "\e[7m%(text)\e[27m" } // reverse video
 
static s(text) { "\e[9m%(text)\e[29m" } // strike out
 
static o(text) { "\e[53m%(text)\e[55m" } // overline
 
}
 
System.print("%(Sgr.c("red", "green", "This")) is a color %(Sgr.c("yellow", "blue", "test")).")
System.print("\nOther effects:")
var effects = [
Sgr.b("Bold"), Sgr.f("Faint"), Sgr.i("Italic"), Sgr.u("Underline"),
Sgr.w("Wink"), Sgr.r("Reverse"), Sgr.s("Strike"), Sgr.o("Overline")
]
System.print(effects.join(", "))