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CHEBEV.PAS
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Pascal/Delphi Source File
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1991-04-29
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530b
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22 lines
FUNCTION chebev(a,b: real; c: glcarray; m: integer; x:real): real;
(* Programs using routine CHEBEV must define the type
glcarray as in routine CHEBFT. *)
VAR
d,dd,sv,y,y2: real;
j: integer;
BEGIN
IF (((x-a)*(x-b)) > 0.0) THEN BEGIN
writeln('pause in CHEBEV - x not in range.'); readln
END;
d := 0.0;
dd := 0.0;
y := (2.0*x-a-b)/(b-a);
y2 := 2.0*y;
FOR j := m DOWNTO 2 DO BEGIN
sv := d;
d := y2*d-dd+c[j];
dd := sv
END;
chebev := y*d-dd+0.5*c[1]
END;