OK ...I now see the wisdom of why Go does not allow my simple example...Thanks ALL for you help on this
On Wed, Aug 7, 2019 at 12:46 PM Adrian Ho <ml+prog-gol...@03s.net> wrote: > On 7/8/19 9:44 PM, lgod...@gmail.com wrote: > > f( g() ) compiles when g returns exactly the number of args that f() > > requires, but if g() returns only 1/2 that number f (g(), g() ) wont > > compile !! ...Is this not a Golang absurdity ?? > > On the contrary, it's a good example of Go's pragmatism, allowing some > relatively safe syntactic sugar without opening a Pandora's box of > complete generality. > > To illustrate Rob Griesemer's point, in his comment that I linked to in > my earlier reply > (https://github.com/golang/go/issues/973#issuecomment-142733515), > consider the following package that's maintained by someone else (your > colleague or an Internet stranger): > > === > > package mu > > func CalcDispersion (in []float64) (variance float64, stddev float64) { > ... } > > func CalcAvg (in []float64) (sma21 float64, ema21 float64) { ... } > > === > > Then you use it as follows, assuming a future Go version that allows > "spreading" of multi-valued function returns: > > === > > v, sd := mu.CalcDispersion(i) > > sma, ema := mu.CalcAvg(i) > > func delta (a, b float64) float64 { return a-b } > > d1 := delta(mu.CalcDispersion(i)) > > d2 := delta(mu.CalcAvg(i)) > > func me (variance float64, stddev float64, sma21 float64, ema21 float64) > float64 { ... } > > m := me(mu.Alpha(i), mu.Beta(i)) > > === > > All well and fine, until one day, the package interface changes after > some discussion: > > === > > package mu > > func CalcDispersion (in []float64) (variance float64, stddev float64, > range float64) { ... } > > func CalcAvg (in []float64) (sma21 float64) { ... } > > === > > Yes, that's a breaking change, and the Go compiler helpfully screams at > you on every assignment statement ...except the last one. And since the > compiler was silent about that last line, you're almost certainly gonna > miss the HUGE logic error in it...and spend days scratching your head at > the absurd results your program throws up. > > -- > Best Regards, > Adrian > > -- > You received this message because you are subscribed to a topic in the > Google Groups "golang-nuts" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/golang-nuts/lFBWugE1nt0/unsubscribe. > To unsubscribe from this group and all its topics, 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/504b90aa-afea-02b7-dfd9-eabf9eace9dc%4003s.net > . > -- 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/CALYe2v4szoy_XMohyegRLZ3GQAfZ3B1W2xhhn9i2fb-9noA8Vg%40mail.gmail.com.
