On 30 Jul 2013, at 22:17, Gerhard Scholz wrote: > Beside of the question, if ++,--,+=,etc. fit into Pascal or not, there stays > the question: is it a plus? > I expected that > a[i] += 3 > compiles better than > a[i] := a[i] + 3 > I expected that the computation of a[i] is done only once, but the produced > code is the same, the address of a[i] is computed twice. > So the whole construct is only a typing saving. > Compilation done with FP 2.6.2, winxp, 32-bit)
Syntax and generated code are in principle unrelated. The reason you don't get the optimised version of the code, is probably because you used global variables. Make the array and i local, and you will see that in both cases the address of a[i] is calculated only once. Constructs involving global variables are harder to analyse for side-effects, so they are simply not optimised at all in many cases by FPC. > Constructs like I++, ++I are nice shortcuts (and sometimes the code can be > better readable), but have only a real value, if the produced code is a bit > optimized. That was true in the eighties when C statements were pretty much directly mapped to assembler. Nowadays, they make code actually harder to optimise because they introduce side-effects in the middle of expressions. Adding a particular syntax to a programming language in order to work around a (realistically solvable) weakness of the optimiser is an extremely bad approach to language design. Jonas_______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
