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{$ifdef win32}
{$H-}
{$endif}
{$ifndef fpc}{$N+}{$endif}
Unit Expr;
interface
const
IntSize2:longbool=false;
PROCEDURE Eval(Formula : String; { Expression to be evaluated}
VAR Value : double; { Return value }
VAR ErrPos : Integer); { error position }
{
Simple recursive expression parser based on the TCALC example of TP3.
Written by Lars Fosdal 1987
Released to the public domain 1993
}
implementation
type
real=double;
PROCEDURE Eval(Formula : String; { Expression to be evaluated}
VAR Value : double; { Return value }
VAR ErrPos : Integer); { error position }
CONST
Digit: Set of Char = ['0'..'9'];
VAR
Posn : Integer; { Current position in Formula}
CurrChar : Char; { character at Posn in Formula }
PROCEDURE ParseNext; { returnerer neste tegn i Formulaen }
BEGIN
REPEAT
Posn:=Posn+1;
IF Posn<=Length(Formula) THEN CurrChar:=Formula[Posn]
ELSE CurrChar:=^M;
UNTIL CurrChar<>' ';
END { ParseNext };
FUNCTION add_subt: Real;
VAR
E : Real;
Opr : Char;
FUNCTION mult_DIV: Real;
VAR
S : Real;
Opr : Char;
FUNCTION Power: Real;
VAR
T : Real;
FUNCTION SignedOp: Real;
FUNCTION UnsignedOp: Real;
TYPE
StdFunc = (fabs, fsqrt, fsqr, fsin, fcos,
farctan, fln, flog, fexp, ffact,
fpred,fsucc,fround,ftrunc);
StdFuncList = ARRAY[StdFunc] of String[6];
CONST
StdFuncName: StdFuncList =
('ABS','SQRT','SQR','SIN','COS',
'ARCTAN','LN','LOG','EXP','FACT',
'PRED','SUCC','ROUND','TRUNC');
VAR
L, Start : Integer;
Funnet : Boolean;
F : Real;
Sf : StdFunc;
FUNCTION Fact(I: Integer): Real;
BEGIN
IF I > 0 THEN BEGIN Fact:=I*Fact(I-1); END
ELSE Fact:=1;
END { Fact };
BEGIN { FUNCTION UnsignedOp }
IF CurrChar in Digit THEN
BEGIN
Start:=Posn;
REPEAT ParseNext UNTIL not (CurrChar in Digit);
IF CurrChar='.' THEN REPEAT ParseNext UNTIL not (CurrChar in Digit);
IF CurrChar='E' THEN
BEGIN
ParseNext;
REPEAT ParseNext UNTIL not (CurrChar in Digit);
END;
Val(Copy(Formula,Start,Posn-Start),F,ErrPos);
END ELSE
IF CurrChar='(' THEN
BEGIN
ParseNext;
F:=add_subt;
IF CurrChar=')' THEN ParseNext ELSE ErrPos:=Posn;
END ELSE
BEGIN
Funnet:=False;
FOR sf:=fabs TO ftrunc DO
IF not Funnet THEN
BEGIN
l:=Length(StdFuncName[sf]);
IF Copy(Formula,Posn,l)=StdFuncName[sf] THEN
BEGIN
Posn:=Posn+l-1; ParseNext;
f:=UnsignedOp{$ifdef fpc}(){$endif};
CASE sf of
fabs: f:=abs(f);
fsqrt: f:=SqrT(f);
fsqr: f:=Sqr(f);
fsin: f:=Sin(f);
fcos: f:=Cos(f);
farctan: f:=ArcTan(f);
fln : f:=LN(f);
flog: f:=LN(f)/LN(10);
fexp: f:=EXP(f);
ffact: f:=fact(Trunc(f));
fpred:f:=f-1;
fsucc:f:=f+1;
fround:f:=round(f)+0.0;
ftrunc:f:=trunc(f)+0.0;
END;
Funnet:=True;
END;
END;
IF not Funnet THEN
BEGIN
ErrPos:=Posn;
f:=0;
END;
END;
UnsignedOp:=F;
END { UnsignedOp};
BEGIN { SignedOp }
IF CurrChar='-' THEN
BEGIN
ParseNext; SignedOp:=-UnsignedOp;
END
ELSE IF CurrChar='!' THEN
BEGIN
ParseNext; SignedOp:=not longint(round(UnsignedOp))+0.0;
END
ELSE SignedOp:=UnsignedOp;
END { SignedOp };
BEGIN { Power }
T:=SignedOp;
WHILE CurrChar='^' DO
BEGIN
ParseNext;
IF t<>0 THEN t:=EXP(LN(abs(t))*SignedOp) ELSE t:=0;
END;
Power:=t;
END { Power };
BEGIN { mult_DIV }
s:=Power;
WHILE CurrChar in ['*','/','&','','\','',''] DO
BEGIN
Opr:=CurrChar; ParseNext;
CASE Opr of
'*': s:=s*Power;
'/': s:=s/Power;
'&': s:=longint(round(s)) and longint(round(power))+0.0;
'': s:=longint(round(s)) mod longint(round(power))+0.0;
'\': s:=trunc(s/Power);
'': s:=longint(round(s)) shl longint(round(power))+0.0;
'': s:=longint(round(s)) shr longint(round(power))+0.0;
END;
END;
mult_DIV:=s;
END { mult_DIV };
BEGIN { add_subt }
E:=mult_DIV;
WHILE CurrChar in ['+','-','|',''] DO
BEGIN
Opr:=CurrChar; ParseNext;
CASE Opr of
'+': e:=e+mult_DIV;
'-': e:=e-mult_DIV;
'|': e:=longint(round(e))or longint(round(mult_DIV))+0.0;
'': e:=longint(round(e))xor longint(round(mult_DIV))+0.0;
END;
END;
add_subt:=E;
END { add_subt };
procedure Replace(const _from,_to:string);
var
p:longint;
begin
repeat
p:=pos(_from,formula);
if p>0 then
begin
delete(formula,p,length(_from));
insert(_to,formula,p);
end;
until p=0;
end;
function HexToDecS:longbool;
var
DecError:longbool;
procedure Decim(const pattern:string);
var
p,b:longint;
x: Longword;
ss,st:string;
begin
repeat
p:=pos(pattern,formula);
if p>0 then
begin
b:=p+length(pattern);
ss:='';
if b<=length(formula)then
begin
while formula[b]in['0'..'9','a'..'f','A'..'F']do
begin
ss:=ss+formula[b];
inc(b);
if b>length(formula)then
break;
end;
val('$'+ss,x,posn);
DecError:=posn<>0;
str(x:0,st);
delete(formula,p,length(pattern)+length(ss));
insert(st,formula,p);
end;
end;
until p=0;
end;
begin
DecError:=false;
Decim('0x');
if not DecError then
Decim('$');
HexToDecS:=not DecError;
end;
BEGIN {PROC Eval}
if not HexToDecS then
begin
value:=0;
ErrPos:=Posn;
exit;
end;
IF Formula[1]='.'
THEN Formula:='0'+Formula;
IF Formula[1]='+'
THEN Delete(Formula,1,1);
FOR Posn:=1 TO Length(Formula)
DO Formula[Posn] := Upcase(Formula[Posn]);
replace('<<','');
replace('>>','');
replace('^','');
replace('**','^');
replace('DIV','\');
replace('MOD','');
replace('AND','&');
replace('XOR','');
replace('SHR','');
replace('SHL','');
replace('NOT','!');
replace('OR','|');
Posn:=0;
ParseNext;
Value:=add_subt;
IF CurrChar=^M THEN ErrPos:=0 ELSE ErrPos:=Posn;
END {PROC Eval};
END.
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