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doc: sorting arrays

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Alexander Medvednikov 2020-08-12 19:14:13 +02:00
parent 3b5d56278f
commit 9478ff472f
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@ -444,7 +444,7 @@ f := 1.0
f1 := f64(3.14) f1 := f64(3.14)
f2 := f32(3.14) 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`.
### Arrays ### Arrays
@ -558,6 +558,24 @@ a[0][1][1] = 2
println(a) // [[[0, 0], [0, 2], [0, 0]], [[0, 0], [0, 0], [0, 0]]] println(a) // [[[0, 0], [0, 2], [0, 0]], [[0, 0], [0, 0], [0, 0]]]
``` ```
#### Sorting arrays
Sorting arrays of all kinds is very simple and intuitive. Special variables `a` and `b`
are used when providing a custom sorting condition.
```v
mut numbers := [1, 3, 2]
numbers.sort() // 1, 2, 3
numbers.sort(a > b) // 3, 2, 1
```
```v
struct User { age int name string }
mut users := [...]
users.sort(a.age < b.age) // sort by User.age int field
users.sort(a.name > b.name) // reverse sort by User.name string field
```
### Maps ### Maps
```v ```v
@ -784,7 +802,7 @@ for i in 0..5 {
print(i) print(i)
} }
``` ```
`low..high` means an *exclusive* range, which represents all values `low..high` means an *exclusive* range, which represents all values
from `low` up to *but not including* `high`. from `low` up to *but not including* `high`.
#### Condition `for` #### Condition `for`
@ -1602,11 +1620,11 @@ fn f(url string) ?string {
} }
``` ```
`http.get` returns `?http.Response`. Because `?` follows the call, the `http.get` returns `?http.Response`. Because `?` follows the call, the
error will be propagated to the caller of `f`. When using `?` after a error will be propagated to the caller of `f`. When using `?` after a
function call producing an optional, the enclosing function must return function call producing an optional, the enclosing function must return
an optional as well. If error propagation is used in the `main()` an optional as well. If error propagation is used in the `main()`
function it will `panic` instead, since the error cannot be propagated function it will `panic` instead, since the error cannot be propagated
any further. any further.
The body of `f` is essentially a condensed version of: The body of `f` is essentially a condensed version of:
@ -1658,7 +1676,7 @@ if resp := http.get(url) {
println(err) println(err)
} }
``` ```
Above, `http.get` returns a `?http.Response`. `resp` is only in scope for the first Above, `http.get` returns a `?http.Response`. `resp` is only in scope for the first
`if` branch. `err` is only in scope for the `else` branch. `if` branch. `err` is only in scope for the `else` branch.
## Generics ## Generics
@ -1705,7 +1723,7 @@ println(compare<string>('1','0')) // Outputs: 1
println(compare<string>('1','1')) // 0 println(compare<string>('1','1')) // 0
println(compare<string>('1','2')) // -1 println(compare<string>('1','2')) // -1
println(compare<float>(1.1, 1.0)) // Outputs: 1 println(compare<float>(1.1, 1.0)) // Outputs: 1
println(compare<float>(1.1, 1.1)) // 0 println(compare<float>(1.1, 1.1)) // 0
println(compare<float>(1.1, 1.2)) // -1 println(compare<float>(1.1, 1.2)) // -1
``` ```
@ -2003,7 +2021,7 @@ fn main(){
## Memory-unsafe code ## Memory-unsafe code
Sometimes for efficiency you may want to write low-level code that can potentially Sometimes for efficiency you may want to write low-level code that can potentially
corrupt memory or be vulnerable to security exploits. V supports writing such code, corrupt memory or be vulnerable to security exploits. V supports writing such code,
but not by default. but not by default.
V requires that any potentially memory-unsafe operations are marked intentionally. V requires that any potentially memory-unsafe operations are marked intentionally.
@ -2035,12 +2053,12 @@ assert *p == `i`
``` ```
Best practice is to avoid putting memory-safe expressions inside an `unsafe` block, Best practice is to avoid putting memory-safe expressions inside an `unsafe` block,
so that the reason for using `unsafe` is as clear as possible. Generally any code so that the reason for using `unsafe` is as clear as possible. Generally any code
you think is memory-safe should not be inside an `unsafe` block, so the compiler you think is memory-safe should not be inside an `unsafe` block, so the compiler
can verify it. can verify it.
If you suspect your program does violate memory-safety, you have a head start on If you suspect your program does violate memory-safety, you have a head start on
finding the cause: look at the `unsafe` blocks (and how they interact with finding the cause: look at the `unsafe` blocks (and how they interact with
surrounding code). surrounding code).
* Note: This is work in progress. * Note: This is work in progress.