Re: [Factor-talk] stack effect

[Iain G. <iai...@ed...>]

many thanks

> On 29 Jul 2015, at 12:04, Björn Lindqvist <bj...@gm...> wrote:
> 
> Georg solved your problem, but in the future you can easily use
> Factors introspection to see why it complains about stack effects. For
> example, the first quotation given to the inner if is [ 0 ] and you
> can infer its stack effect:
> 
> IN: scratchpad [ 0 ] infer.
> ( -- x )
> 
> Then because the two quotations given to if must have the same stack
> effect, the second quotation must also have ( -- x ) which you can
> check like this:
> 
> ! Needs to be declared because you are using locals
> IN: scratchpad SYMBOLS: amount coins cc denominations ;
> IN: scratchpad [ amount coins 1 - cc amount coins denominations at*
> drop - coins cc + ] infer.
> ( -- x x x x x )
> 
> Or you can manually count the stack delta. Local variables and numbers
> are +1, binary operations and drop -1 and at* is +/- 0:
>  +1     +1    +1 -1 +1 +1     +1    +1            0   -1   -1 +1    +1 -1
> [ amount coins 1  -  cc amount coins denominations at* drop -  coins cc +  ]
> 
> 1 + 1 + 1 - 1 + 1 + 1 + 1 + 1 + 0 - 1 - 1 + 1 + 1 - 1 = +5
> 
> 2015-07-29 9:44 GMT+02:00 Iain Gray <iai...@ed...>:
>> why do I get the following error?
>> 
>> Stack effect declaration is wrong
>> inferred ( x x x -- x x )
>> declared ( amount coins -- ways )
>> 
>> from this lexical variable
>> 
>> :: cc ( amount coins -- ways )
>>    0 amount = [ 1 ]
>>    [ 0 < amount 0 coins = or [ 0 ]
>>      [ amount coins 1 - cc
>>        amount coins denominations at* drop - coins cc + ]
>>      if ]
>>      if ;
>> 
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> 
> 
> 
> -- 
> mvh/best regards Björn Lindqvist
> 
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