Function and procedure behave differently with the same code in Mozart Oz? -

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i try printing out fibonacci sequence in oz using 2 approach : function , procedure using emac editor. procedure goes here :

declare  fun {fibo n}     case n of        1 1     [] 2 1 [] m {fibo (m-1)} + {fibo (m-2)}     end  end  declare proc {loop k}    if k ==1  {browse k}    else       {loop k-1}        {browse {fibo k}}    end end {loop 10}

and function:

declare  fun {fibo n}     case n of        1 1     [] 2 1 [] m {fibo (m-1)} + {fibo (m-2)}     end  end declare fun {loo l}    if l ==1  {browse l}    else       {loo l-1}        {browse {fibo l}}    end end {loo 10}

the problem procedure "loop" works. result is:

1 1 2 3 5 8 13 21 34 55

function "loo" doesn't , throws hard-to-understand errors:

%********************** static analysis error ******************* %** %** illegal arity in application %** %** arity found:          1 %** expected:             2 %** application (names):  {loo _} %** application (values): {<p/2> _<optimized>} %** in file "oz", line 13, column 6  %********************** static analysis error ******************* %** %** illegal arity in application %** %** arity found:          1 %** expected:             2 %** application (names):  {loo _} %** application (values): {<p/2> 10} %** in file "oz", line 17, column 0 %** ------------------ rejected (2 errors)

i still don't know why. think function , procedure has similar effect in oz.

functions must called either function call syntax:

_ = {loo 10}

or alternatively additional parameter receive value:

{loo 10 _}

_ pronounced "don't care" , means value of variable not needed.

also, functions must return value having expression last part of every branch. fixed loo function this:

fun {loo l}    if l == 1       {browse l}       unit    else       _ = {loo l-1}       {browse {fibo l}}       unit    end end _ = {loo 10}

however, using function looping not make sense if don't have interesting return. maybe want build list , return result?


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