but that would enable or disable _all_ precondition checks.
What I am looking for is soth. smart enough that deduces that the
precondition checks in `mul` and `add` can be removed because of the
precondition check in `Muladd`.
On Thursday, March 31, 2022 at 5:26:44 AM UTC+2 Henry wrote:
> You will need a build tag for that.
>
> For example:
>
> In a separate file, define the build tag
> ```
> // +build debug
>
> package mypkg
>
> func init() {
> Debug = true
> }
> ```
> Then, in other files, use the tag
> ```
> package mypkg
>
> var Debug bool
>
> func DoWork() {
> if Debug {
> // perform validation
> }
> }
> ```
> When building with validation, call "go build -tags debug"
> On Thursday, March 31, 2022 at 1:40:07 AM UTC+7 toon....@gmail.com wrote:
>
>> I like to check the preconditions of a function explicitly by means of
>> code (instead of only documenting them). Of course this incurs a
>> time-penalty.
>>
>> When being extremely cautious every function in a call-chain will always
>> check its preconditions. But for a function down in the call-chain, the
>> precondition checks of all its callers might already guarantee that its own
>> pre-condition checks will never be violated. And thus these checks down the
>> chain are unnecessary cpu cycles.
>>
>> Do there exist tools/methods to detect this and auto-remove these
>> precondition checks?
>>
>> For example:
>> the function Muladd below verifies that all arrays have the same length.
>> Muladd relies on two functions to perform the `mul` and the `add` and each
>> of these will also verify their respective preconditions explicitly. Given
>> these functions are not exported and given these functions are only called
>> by `muladd`, the compiler might be able to determine that the precondition
>> checks are guaranteed to be valid and can thus be removed.
>>
>> https://go.dev/play/p/92isKKx-vYx
>>
>> package main
>>
>> import "fmt"
>>
>> func main() {
>> x := []float64{1.0, 2.0, 3.0}
>> y := []float64{1.0, 2.0, 3.0}
>> z := []float64{1.0, 2.0, 3.0}
>> Muladd(x, y, z)
>> fmt.Printf("%+v", x)
>> }
>>
>> func Muladd(x []float64, y []float64, z []float64) error {
>> // check precondition (but unnecessary if only called by Muladd)
>> if len(x) != len(y) || len(x) != len(z) {
>> return fmt.Errorf("slices have different lengths %d vs %d vs %d",
>> len(x), len(y), len(z))
>> }
>> mul(x, y)
>> add(x, z)
>> return nil
>> }
>>
>> func mul(x []float64, y []float64) error {
>> // check precondition
>> if len(x) != len(y) {
>> return fmt.Errorf("slices have different lengths %d vs %d",
>> len(x), len(y))
>> }
>>
>> for i := range x {
>> x[i] *= y[i]
>> }
>> return nil
>> }
>>
>> func add(x []float64, y []float64) error {
>> // check precondition
>> if len(x) != len(y) {
>> return fmt.Errorf("slices have different lengths %d vs %d",
>> len(x), len(y))
>> }
>>
>> for i := range x {
>> x[i] += y[i]
>> }
>> return nil
>> }
>>
>
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/23966f0a-4ee9-4733-a4c0-ba1a4964d5f8n%40googlegroups.com.
