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docs: float exponential syntax (#10973)

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Lukas Neubert 2021-07-28 07:21:42 +02:00 committed by GitHub
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@ -624,6 +624,13 @@ f2 := f32(3.14)
If you do not specify the type explicitly, by default float literals If you do not specify the type explicitly, by default float literals
will have the type of `f64`. will have the type of `f64`.
Float literals can also be declared as a power of ten:
```v
f0 := 42e1 // 420
f1 := 123e-2 // 1.23
f2 := 456e+2 // 45600
```
### Arrays ### Arrays
#### Basic Array Concepts #### Basic Array Concepts
Arrays are collections of data elements of the same type. They can be represented by Arrays are collections of data elements of the same type. They can be represented by
@ -3730,7 +3737,7 @@ fn f() (RefStruct, &MyStruct) {
Here `a` is stored on the stack since it's address never leaves the function `f()`. Here `a` is stored on the stack since it's address never leaves the function `f()`.
However a reference to `b` is part of `e` which is returned. Also a reference to However a reference to `b` is part of `e` which is returned. Also a reference to
`c` is returned. For this reason `b` and `c` will be heap allocated. `c` is returned. For this reason `b` and `c` will be heap allocated.
Things become less obvious when a reference to an object is passed as function argument: Things become less obvious when a reference to an object is passed as function argument:
@ -3763,7 +3770,7 @@ these references are leaving `main()`. However the *lifetime* of these
references lies inside the scope of `main()` so `q` and `w` are allocated references lies inside the scope of `main()` so `q` and `w` are allocated
on the stack. on the stack.
#### Manual Control for Stack and Heap #### Manual Control for Stack and Heap
In the last example the V compiler could put `q` and `w` on the stack In the last example the V compiler could put `q` and `w` on the stack
because it assumed that in the call `q.f(&w)` these references were only because it assumed that in the call `q.f(&w)` these references were only
@ -3811,7 +3818,7 @@ reference to `s` into `r`. The problem with this is that `s` lives only as long
as `g()` is running but `r` is used in `main()` after that. For this reason as `g()` is running but `r` is used in `main()` after that. For this reason
the compiler would complain about the assignment in `f()` because `s` *"might the compiler would complain about the assignment in `f()` because `s` *"might
refer to an object stored on stack"*. The assumption made in `g()` that the call refer to an object stored on stack"*. The assumption made in `g()` that the call
`r.f(&s)` would only borrow the reference to `s` is wrong. `r.f(&s)` would only borrow the reference to `s` is wrong.
A solution to this dilemma is the `[heap]` attribute at the declaration of A solution to this dilemma is the `[heap]` attribute at the declaration of
`struct MyStruct`. It instructs the compiler to *always* allocate `MyStruct`-objects `struct MyStruct`. It instructs the compiler to *always* allocate `MyStruct`-objects
@ -4396,7 +4403,7 @@ If no flags are passed it will add `--cflags` and `--libs`, both lines below do
The `.pc` files are looked up into a hardcoded list of default pkg-config paths, the user can add The `.pc` files are looked up into a hardcoded list of default pkg-config paths, the user can add
extra paths by using the `PKG_CONFIG_PATH` environment variable. Multiple modules can be passed. extra paths by using the `PKG_CONFIG_PATH` environment variable. Multiple modules can be passed.
To check the existance of a pkg-config use `$pkgconfig('pkg')` as a compile time if condition to To check the existance of a pkg-config use `$pkgconfig('pkg')` as a compile time if condition to
check if a pkg-config exists. If it exists the branch will be created. Use `$else` or `$else $if` check if a pkg-config exists. If it exists the branch will be created. Use `$else` or `$else $if`
to handle other cases. to handle other cases.