[fpc-pascal] String conversions

[Ben Grasset]

On Wed, Jun 26, 2019 at 3:28 PM Ben Grasset <operator97 at gmail.com> wrote:

> I think Ryan probably meant his own custom types. And certainly, you can
> do some interesting stuff with operator overloading that mostly avoids the
> normal AnsiString overhead. Here's an example.
> <https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(j:1,lang:pascal,source:'unit+output%3B%0A%0A%7B$mode+ObjFPC%7D%7B$H%2B%7D%0A%7B$modeswitch+AdvancedRecords%7D%0A%7B$ImplicitExceptions+Off%7D%0A%0Ainterface%0A%0Atype+%0A++TPCharEx+%3D+record%0A++++P:+PChar%3B%0A++++L:+SizeInt%3B%0A++++class+operator+:%3D(constref+LHS:+AnsiString):+TPCharEx%3B+inline%3B%0A++++class+operator+:%3D(constref+LHS:+ShortString):+TPCharEx%3B+inline%3B%0A++end%3B%0A%0Afunction+Reversed(constref+P:+TPCharEx):+AnsiString%3B%0Aprocedure+ImplicitConversionTest%3B+inline%3B%0A%0Aimplementation%0A%0Aclass+operator+TPCharEx.:%3D(constref+LHS:+AnsiString):+TPCharEx%3B%0Abegin%0A++with+Result+do+begin%0A++++P+:%3D+ at LHS%5B1%5D%3B%0A++++L+:%3D+Length(LHS)%3B%0A++end%3B%0Aend%3B%0A%0Aclass+operator+TPCharEx.:%3D(constref+LHS:+ShortString):+TPCharEx%3B%0Abegin%0A++with+Result+do+begin%0A++++P+:%3D+ at LHS%5B1%5D%3B%0A++++L+:%3D+Ord(LHS%5B0%5D)%3B%0A++end%3B%0Aend%3B%0A%0Afunction+Reversed(constref+P:+TPCharEx):+AnsiString%3B%0Avar+Old,+New:+PChar%3B%0Abegin%0A++SetLength(Result,+P.L+%2B+1)%3B%0A++Old+:%3D+P.P+%2B+P.L%3B%0A++New+:%3D+ at Result%5B1%5D%3B%0A++while+Old+%3E%3D+P.P+do+begin%0A++++New%5E+:%3D+Old%5E%3B%0A++++Inc(New)%3B%0A++++Dec(Old)%3B%0A++end%3B%0Aend%3B%0A%0Aprocedure+ImplicitConversionTest%3B%0Abegin%0A++WriteLn(Reversed(!'ABCD!'))%3B%0Aend%3B%0A%0Aend.%0A'),l:'5',n:'0',o:'Pascal+source+%231',t:'0')),k:54.64556642679632,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:compiler,i:(compiler:fpc304,filters:(b:'0',binary:'1',commentOnly:'0',demangle:'0',directives:'0',execute:'0',intel:'0',libraryCode:'1',trim:'1'),lang:pascal,libs:!(),options:'-O3+-Ci-+-Cr-+-g-+-CX+-XXs',source:1),l:'5',n:'0',o:'x86-64+fpc+3.0.4+(Editor+%231,+Compiler+%231)+Pascal',t:'0')),k:44.015665176626996,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:output,i:(compiler:1,editor:1,wrap:'1'),l:'5',n:'0',o:'%231+with+x86-64+fpc+3.0.4',t:'0')),k:1.3387683965766675,l:'4',n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4>
>

Messed up the "Reversed" function a little bit in that example. Fixed
version.
<https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(j:1,lang:pascal,source:'unit+output%3B%0A%0A%7B$mode+ObjFPC%7D%7B$H%2B%7D%0A%7B$modeswitch+AdvancedRecords%7D%0A%7B$ImplicitExceptions+Off%7D%0A%0Ainterface%0A%0Atype+%0A++TPCharEx+%3D+record%0A++++P:+PChar%3B%0A++++L:+SizeInt%3B%0A++++class+operator+:%3D(constref+LHS:+AnsiString):+TPCharEx%3B+inline%3B%0A++++class+operator+:%3D(constref+LHS:+ShortString):+TPCharEx%3B+inline%3B%0A++end%3B%0A%0Afunction+Reversed(constref+P:+TPCharEx):+AnsiString%3B%0Aprocedure+ImplicitConversionTest%3B+inline%3B%0A%0Aimplementation%0A%0Aclass+operator+TPCharEx.:%3D(constref+LHS:+AnsiString):+TPCharEx%3B%0Abegin%0A++with+Result+do+begin%0A++++P+:%3D+ at LHS%5B1%5D%3B%0A++++L+:%3D+Length(LHS)%3B%0A++end%3B%0Aend%3B%0A%0Aclass+operator+TPCharEx.:%3D(constref+LHS:+ShortString):+TPCharEx%3B%0Abegin%0A++with+Result+do+begin%0A++++P+:%3D+ at LHS%5B1%5D%3B%0A++++L+:%3D+Ord(LHS%5B0%5D)%3B%0A++end%3B%0Aend%3B%0A%0Afunction+Reversed(constref+P:+TPCharEx):+AnsiString%3B%0Avar+Old,+New:+PChar%3B%0Abegin%0A++SetLength(Result,+P.L)%3B%0A++Old+:%3D+P.P+%2B+P.L+-+1%3B%0A++New+:%3D+ at Result%5B1%5D%3B%0A++while+Old+%3E%3D+P.P+do+begin%0A++++New%5E+:%3D+Old%5E%3B%0A++++Inc(New)%3B%0A++++Dec(Old)%3B%0A++end%3B%0Aend%3B%0A%0Aprocedure+ImplicitConversionTest%3B%0Abegin%0A++WriteLn(Reversed(!'ABCD!'))%3B%0Aend%3B%0A%0Aend.%0A'),l:'5',n:'0',o:'Pascal+source+%231',t:'0')),k:54.64556642679632,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:compiler,i:(compiler:fpc304,filters:(b:'0',binary:'1',commentOnly:'0',demangle:'0',directives:'0',execute:'0',intel:'0',libraryCode:'1',trim:'1'),lang:pascal,libs:!(),options:'-O3+-Ci-+-Cr-+-g-+-CX+-XXs',source:1),l:'5',n:'0',o:'x86-64+fpc+3.0.4+(Editor+%231,+Compiler+%231)+Pascal',t:'0')),k:44.015665176626996,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:output,i:(compiler:1,editor:1,wrap:'1'),l:'5',n:'0',o:'%231+with+x86-64+fpc+3.0.4',t:'0')),k:1.3387683965766675,l:'4',n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4>
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