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(* ConvStringReal.mod translate floating point numbers to Strings.
Copyright (C) 2009-2025 Free Software Foundation, Inc.
Contributed by Gaius Mulley <gaius.mulley@southwales.ac.uk>.
This file is part of GNU Modula-2.
GNU Modula-2 is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GNU Modula-2 is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. *)
IMPLEMENTATION MODULE ConvStringReal ;
FROM DynamicStrings IMPORT InitString, KillString, ConCat, ConCatChar,
Slice, Length, Mult, Mark, InitStringCharStar,
InitStringChar, Index, char ;
FROM StringConvert IMPORT IntegerToString, ToSigFig ;
FROM dtoa IMPORT dtoa, Mode ;
FROM libc IMPORT free, printf ;
FROM SYSTEM IMPORT ADDRESS ;
CONST
Debugging = FALSE ;
(*
IsDigit - returns TRUE if, ch, lies between '0'..'9'.
*)
PROCEDURE IsDigit (ch: CHAR) : BOOLEAN ;
BEGIN
RETURN (ch>='0') AND (ch<='9')
END IsDigit ;
(*
RealToFloatString - converts a real with, sigFigs, into a string
and returns the result as a string.
*)
PROCEDURE RealToFloatString (real: REAL; sigFigs: CARDINAL) : String ;
VAR
point, l,
powerOfTen: INTEGER ;
s : String ;
r : ADDRESS ;
sign : BOOLEAN ;
BEGIN
r := dtoa(real, maxsignificant, 100, point, sign) ;
s := InitStringCharStar(r) ;
free(r) ;
IF sigFigs>0
THEN
l := Length(s) ;
IF (l>0) AND IsDigit(char(s, 0))
THEN
IF VAL(INTEGER, sigFigs)<l
THEN
s := Slice(ToSigFig(s, sigFigs), 0, sigFigs)
ELSE
(* add '0's to make up significant figures *)
s := ConCat(s, Mark(Mult(InitStringChar('0'), l-VAL(INTEGER, sigFigs))))
END ;
l := Length(s) ;
(*
* we reassign point to 1 and adjust the exponent
* accordingly, so we can achieve the format X.XXXE+X
*)
powerOfTen := point-1 ;
point := 1 ;
IF (point<l) AND (point<VAL(INTEGER, sigFigs))
THEN
s := ConCat(ConCatChar(Slice(s, 0, point), '.'),
Slice(s, point, 0))
END ;
IF powerOfTen#0
THEN
s := ConCat(ConCatChar(s, 'E'),
IntegerToString(powerOfTen, 0, ' ', TRUE, 10, FALSE))
END
END ;
IF sign
THEN
s := ConCat(InitStringChar('-'), Mark(s))
END
END ;
RETURN( s )
END RealToFloatString ;
(*
RealToEngString - converts the value of real to floating-point
string form, with sigFigs significant figures.
The number is scaled with one to three digits
in the whole number part and with an exponent
that is a multiple of three.
*)
PROCEDURE RealToEngString (real: REAL; sigFigs: CARDINAL) : String ;
VAR
offset,
point,
powerOfTen: INTEGER ;
s : String ;
l : CARDINAL ;
r : ADDRESS ;
sign : BOOLEAN ;
BEGIN
r := dtoa(real, maxsignificant, 100, point, sign) ;
s := InitStringCharStar(r) ;
free(r) ;
IF sigFigs>0
THEN
l := Length(s) ;
IF (l>0) AND IsDigit(char(s, 0))
THEN
IF sigFigs<l
THEN
s := Slice(ToSigFig(s, sigFigs), 0, sigFigs)
ELSE
(* add '0's to make up significant figures *)
s := ConCat(s, Mark(Mult(InitStringChar('0'), l-sigFigs)))
END ;
l := Length(s) ;
IF (point>0) AND (point<=2)
THEN
(* current range is fine, no need for a exponent *)
powerOfTen := 0 ;
IF point>VAL(INTEGER, sigFigs)
THEN
(* add '0's to make up required mantissa length *)
s := ConCat(s, Mark(Mult(InitStringChar('0'), point-VAL(INTEGER, sigFigs)))) ;
l := Length(s)
END
ELSE
(*
* desire a value of point which lies between 1..3
* this allows the mantissa to have the format
* X.XXX or XX.XX or XXX.X
*)
powerOfTen := point-VAL(INTEGER, l) ;
point := point-powerOfTen ;
offset := 0 ;
IF point>3
THEN
offset := (point DIV 3) * 3 ;
point := point-offset ;
powerOfTen := powerOfTen+offset
ELSIF point<0
THEN
offset := (ABS(point) DIV 3) * 3 ;
point := point+offset ;
powerOfTen := powerOfTen-offset
END ;
IF powerOfTen<0
THEN
IF ABS(powerOfTen) MOD 3#0
THEN
offset := 3-(ABS(powerOfTen) MOD 3)
END
ELSE
(* at this stage, point >= sigFigs *)
IF powerOfTen MOD 3#0
THEN
offset := -(3-(powerOfTen MOD 3))
END
END ;
IF offset+point>VAL(INTEGER, sigFigs)
THEN
(* add '0's to make up required mantissa length *)
s := ConCat(s, Mark(Mult(InitStringChar('0'), offset+point-VAL(INTEGER, sigFigs)))) ;
l := Length(s)
END ;
(* now adjust point and powerOfTen by offset *)
point := point + offset ;
powerOfTen := powerOfTen - offset
END ;
IF point<0
THEN
s := ConCat(ConCat(InitString('0.'), Mult(InitStringChar('0'), -point)), s)
ELSIF (point>0) AND (point<VAL(INTEGER, l)) AND (point<VAL(INTEGER, sigFigs))
THEN
s := ConCat(ConCatChar(Slice(s, 0, point), '.'),
Slice(s, point, 0))
END ;
IF powerOfTen#0
THEN
s := ConCat(ConCatChar(s, 'E'),
IntegerToString(powerOfTen, 0, ' ', TRUE, 10, FALSE))
END
END ;
IF sign
THEN
s := ConCat(InitStringChar('-'), Mark(s))
END
END ;
RETURN( s )
END RealToEngString ;
(*
RealToFixedString - returns the number of characters in the fixed-point
string representation of real rounded to the given
place relative to the decimal point.
*)
PROCEDURE RealToFixedString (real: REAL; place: INTEGER) : String ;
VAR
l,
point: INTEGER ;
sign : BOOLEAN ;
r : ADDRESS ;
s : String ;
BEGIN
r := dtoa(real, maxsignificant, 100, point, sign) ;
s := InitStringCharStar(r) ;
free(r) ;
l := Length(s) ;
IF Debugging
THEN
printf("length of string returned is %d decimal point at position %d\n", l, point)
END ;
IF (l>0) AND IsDigit(char(s, 0))
THEN
IF point+place>=0
THEN
(* add decimal point at correct position *)
IF point<0
THEN
s := ConCat(ConCat(InitString('0.'), Mult(InitStringChar('0'), -point)), s)
ELSIF point=0
THEN
s := ConCat(InitString('0.'), Mark(s))
ELSIF point<l
THEN
s := ConCat(ConCatChar(Slice(s, 0, point), '.'),
Slice(s, point, 0))
END ;
IF place<0
THEN
s := ToSigFig(s, point+place+1)
ELSE
s := ToSigFig(s, point+place)
END ;
l := Length(s) ;
IF place>=0
THEN
IF Index(s, '.', 0)<0
THEN
s := ConCatChar(s, '.') ;
s := ConCat(s, Mark(Mult(InitStringChar('0'), place)))
ELSE
point := Index(s, '.', 0) ;
IF l-point<place
THEN
s := ConCat(s, Mark(Mult(InitStringChar('0'), l-point-place)))
END
END
END
ELSE
IF place<0
THEN
s := InitString('0')
ELSIF place=0
THEN
s := InitString('0.')
ELSE
s := InitString('0.0')
END
END
END ;
IF sign
THEN
s := ConCat(InitStringChar('-'), Mark(s))
END ;
RETURN( s )
END RealToFixedString ;
END ConvStringReal.
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