4 ms·

Yes. Anointing "+ 1" as a thing that needs special syntax is weird.

dragonwriter 11y ago
> Yes. Anointing "+ 1" as a thing that needs special syntax is weird. Its not a special syntax for "+1", its a special syntax for the combination of assignment and increment/decrement. The postfix versions (increment/decrement variable and then return the value that was present before the increment/decrement), particularly, are equivalent to: _x = x; x += 1; _x In an environment where that pattern of operations is common, I can see the value of having a concise mechanism for expressing it. OTOH, there's a cost to it, too, and I'm mostly happier without them around.
- cballard 11y ago
  Sorry, you are correct - although I would restate my point with "+= 1" isn't special. 1 is just another number, the fact that it's useful for enumerating arrays in C isn't relevant as Swift provides more native solutions for that, the use of which should be encouraged.
ars 11y ago
Have you never heard the rule that your code should have no numbers in it except 0 and 1? All other numbers should be written as constants instead, and then use the name of the constant instead of the number directly. > Anointing "+ 1" as a thing that needs special syntax is weird. 1 is special.
- cballard 11y ago
  Yes, of course, I use constants in all cases. Why is adding 1 to something special, compared to adding 2 to something? The #1 use case, by far, is C-style for loops, which aren't used in idiomatic Swift code.
  - ars 11y ago
    I said why: The 2 should be a constant as a name, but the 1 can be a bare 1.
spc476 11y ago
Not necessarily so if you come from a strong Assembly language background. Most processors have a special instruction for incrementing a register that's shorter (and faster) than the more generic ADD instruction. For instance, on a 64-bit x86 machine, ADD RAX,1 is nine bytes long, while INC RAX is one byte. Maybe not as much a win these days, but back when memory was smaller and more expensive, it was worth it.
- cballard 11y ago
  In a high-level language, this is the job of the compiler, though. If the compiler isn't generating those instructions for cases where the increment can be proven to be 1, I would consider it a bug.
- DiThi 11y ago
  Nowadays, a compiler that doesn't optimize a "+1" is a bad compiler.
  - spc476 11y ago
    These days yes. But when C was first being developed, when you might have had 64K of memory for everything? Back then it might have been a sane choice.
- JoeAltmaier 11y ago
  Doesn't x86 machine code have short-immediate forms? So ADD RAX,1 could be 4 or 5 bytes. Still a win to use INC of course.
- throwaway999888 11y ago
  Any optimising compiler for a mainstream language that can't do this optimisation reliably in this day and age is crap.
- mattst88 11y ago
  Compiling #include <stdint.h> uint64_t inc(uint64_t x) { return x + 1; } With -O0 gives me: 48 83 c0 01 add $0x1,%rax and with -O2: 48 8d 47 01 lea 0x1(%rdi),%rax That is, both are four bytes.

> Yes. Anointing "+ 1" as a thing that needs special syntax is weird. Its not a special syntax for "+1", its a special syntax for the combination of assignment and increment/decrement. The postfix versions (increment/decrement variable and then return the value that was present before the increment/decrement), particularly, are equivalent to: _x = x; x += 1; _x In an environment where that pattern of operations is common, I can see the value of having a concise mechanism for expressing it. OTOH, there's a cost to it, too, and I'm mostly happier without them around.

cballard 11y ago
Sorry, you are correct - although I would restate my point with "+= 1" isn't special. 1 is just another number, the fact that it's useful for enumerating arrays in C isn't relevant as Swift provides more native solutions for that, the use of which should be encouraged.

ars 11y ago

Have you never heard the rule that your code should have no numbers in it except 0 and 1? All other numbers should be written as constants instead, and then use the name of the constant instead of the number directly. > Anointing "+ 1" as a thing that needs special syntax is weird. 1 is special.

cballard 11y ago
Yes, of course, I use constants in all cases. Why is adding 1 to something special, compared to adding 2 to something? The #1 use case, by far, is C-style for loops, which aren't used in idiomatic Swift code.
- ars 11y ago
  I said why: The 2 should be a constant as a name, but the 1 can be a bare 1.

spc476 11y ago

Not necessarily so if you come from a strong Assembly language background. Most processors have a special instruction for incrementing a register that's shorter (and faster) than the more generic ADD instruction. For instance, on a 64-bit x86 machine, ADD RAX,1 is nine bytes long, while INC RAX is one byte. Maybe not as much a win these days, but back when memory was smaller and more expensive, it was worth it.

cballard 11y ago
In a high-level language, this is the job of the compiler, though. If the compiler isn't generating those instructions for cases where the increment can be proven to be 1, I would consider it a bug.
DiThi 11y ago
Nowadays, a compiler that doesn't optimize a "+1" is a bad compiler.
- spc476 11y ago
  These days yes. But when C was first being developed, when you might have had 64K of memory for everything? Back then it might have been a sane choice.
JoeAltmaier 11y ago
Doesn't x86 machine code have short-immediate forms? So ADD RAX,1 could be 4 or 5 bytes. Still a win to use INC of course.
throwaway999888 11y ago
Any optimising compiler for a mainstream language that can't do this optimisation reliably in this day and age is crap.
mattst88 11y ago
Compiling #include <stdint.h> uint64_t inc(uint64_t x) { return x + 1; } With -O0 gives me: 48 83 c0 01 add $0x1,%rax and with -O2: 48 8d 47 01 lea 0x1(%rdi),%rax That is, both are four bytes.