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(* Prozeduren zur Ausgabe auf ASCII-Terminals *)
INT CONST up := 1 ,
right := 1 ,
down := -1 ,
left := -1 ;
INT VAR x pos := 0 ,
y pos := 0 ,
new x pos ,
new y pos ;
BOOL VAR plot := FALSE;
TEXT CONST empty line :: 79 * " ";
ROW 24 TEXT VAR display;
PROC plot vector (INT CONST dx , dy) :
IF dx >= 0
THEN IF dy > dx THEN vector (y pos, x pos, dy, dx, up, right)
ELIF dy > 0 THEN vector (x pos, y pos, dx, dy, right, up)
ELIF dy > -dx THEN vector (x pos, y pos, dx, -dy, right, down)
ELSE vector (y pos, x pos, -dy, dx, down, right)
FI
ELSE IF dy > -dx THEN vector (y pos, x pos, dy, -dx, up, left)
ELIF dy > 0 THEN vector (x pos, y pos, -dx, dy, left, up)
ELIF dy > dx THEN vector (x pos, y pos, -dx, -dy, left, down)
ELSE vector (y pos, x pos, -dy, -dx, down, left)
FI
FI .
ENDPROC plot vector ;
PROC vector (INT VAR x pos, y pos, INT CONST dx, dy, right, up) :
prepare first step ;
INT VAR i ;
FOR i FROM 1 UPTO dx REP
do one step
PER .
prepare first step :
point;
INT VAR old error := 0 ,
up right error := dy - dx ,
right error := dy .
do one step :
IF right is better
THEN do right step
ELSE do up right step
FI .
right is better :
abs (old error + right error) < abs (old error + up right error) .
do upright step :
x pos INCR right ;
y pos INCR up ;
point ;
old error INCR upright error .
do right step :
x pos INCR right ;
point ;
old error INCR right error .
ENDPROC vector ;
PROC point :
IF x pos < 1
THEN x pos := 1
ELIF x pos > 78
THEN x pos := 78 FI;
IF y pos < 1
THEN y pos := 1
ELIF y pos > 47
THEN y pos := 47 FI;
INT CONST line :: y pos DIV 2;
BOOL CONST above :: (y pos MOD 2) = 1;
TEXT CONST point :: display [line+1] SUB (x pos+1),
new point :: calculated point;
replace (display [line+1], x pos+1, new point);
cursor (x pos, 24-line);
out (new point) .
calculated point :
IF above
THEN IF point = "," OR point = "|"
THEN "|"
ELSE "'" FI
ELSE IF point = "'" OR point = "|"
THEN "|"
ELSE "," FI
FI
END PROC point;
REAL CONST real max int := real (max int);
INT PROC round (REAL CONST x) :
IF x > real max int
THEN max int
ELIF x < 0.0
THEN 0
ELSE int (x + 0.5) FI
END PROC round;
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