Re: [fpc-pascal] Currency constant wrongly stored in generated EXE?
Lets restate the hole thing, considering unit ncon.pas and pexpr.pas units
in FPC 2.6.4
compiler.
1° It is not possible, without using some ad hoc adjustements, to have
always an EXACT CURRENCY stored in a DOUBLE or EXTENDED because Double or
Extended being expressed as Sign*2^exp*Base2(n). Just start with 0.1 to see
what I mean.
2° trealconstnode class stores the currency_literal value to value_real
(type bestreal) then converts it to value_currency either in the
trealconstnode.create or sets it in pexpr.pas function
factor(getaddr,typeonly:boolean) : tnode; just after {$ifdef
FPC_HAS_STR_CURRENCY}
3° c:=92233720368547; // The original problem
multiple operations involve *1 (OK per see) and /1 (not so good)
while parsing the constant to bestreal type before generating .EXE code.
(bestreal is Extended on Intel I386 and Up and Double on ARM).
4° The compiler will not compain about Currency_Value:=0.9 whereas the
max decimal precision is 0. for decimal part.
5° What I found is that only + or - operations on Currency's giving a
Currency will be generated with plain Int64 addition and subtractions.
Now what ?
It would be interesting that someone who has an ARM based machine/compiler
do
some testing.
Since currency is a very good type for accounting, you know
Sum(Assets)-Sum(Liabilities)=Sum(Incomes)-Sum(Costs) - hopefully benefit
and exact,
some workarounds must be found.
A basic way to circumvent the risks when absolutly necessary would be
something like what is decribed next, not very Pascal clean I must admit :
- Insure that the compiler will not see a literal currency when assigning or
calculating a precise value containing a literal currency value.
so short example, look at the ASM code generated.
var
c: currency;
lInt64:Int64 absolute c; // Avoid use of Currency
begin
c:=0.9; // Accepted by the compiler ... and rounded to 1
c:=0.99986; // Accepted by the compiler ... and rounded to 0.
c:=0.99984; // Accepted by the compiler ... and rounded to 0.9998
{ The easy way but uses the FPU }
c:=92233720368547; // - that might be wrongly evaluated by the Compiler
(FPU usage) but nothing will be visible in the generated ASM regarding FPU
evaluation, except in your case, an invalid HEX value
c:=c+0.01; // - uses FPU
writeln('c+0.01 with FPU=', c);
{ Clumsy but no FPU usage while compiling and executing }
lInt64:=92233720368547; // - You can test but my bet is that it
probably always correctly evaluated by the compiler
lInt64:=lInt64+100; // Equivalent to c:=c+0.01
writeln('c+0.01 indirect no FPU=', c);
readln;
end;
Your subject has been interesting and I'll be careful now with rounding and
Currency.
Regard Bruno.
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[fpc-pascal] EventLog and error No member is provided to access property
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Re: [fpc-pascal] 2.6.4 RPM and Deb archives are still in preparation?
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[fpc-pascal] [ANN] Brook 3.0.0 release!
The Brook team is glad to announce the release 3.0.0. This version was compiled and tested successfully with Free Pascal 2.6.4. Here is the list of changes between version 2.6.4 and 3.0.0 of the Brook: https://github.com/silvioprog/brookframework/compare/57f8e01868dbec9708129bc789940df2a93c1637...v3.0.0 (or short URL here:http://goo.gl/kr9oX0) The release is available for download on Github: https://github.com/silvioprog/brookframework/releases/tag/v3.0.0 Or through the Latest Release button on the project home page: http://silvioprog.github.io/brookframework/ Minimum requirements: Free Pascal 2.6.4. If you prefer the Lazarus interface, choose the 1.2.2 version. Enjoy! -- Silvio Clécio My public projects - github.com/silvioprog ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] How to get GO32 Unit file
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