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Re: [Maxima-discuss] using return within a for loop within a function
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From: andre m. <and...@gm...> - 2019-05-02 20:46:02
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looks like I'm going to write a small shell script
with some added sed code around my maxima invocations
Thanks
Andre
On 5/2/19 9:13 PM, Stavros Macrakis (Σταῦρος Μακράκης) wrote:
> As Barton said, we already have catch/throw. You can write:
>
> myfunc(...):=catch( ...
> ... throw(result) ...)
>
> If you really want, you could easily define a macro tblock (throw-block)
> which is equivalent to catch(block(...)).
>
> The main problem with all of Maxima's throw and return mechanisms is that
> there is no way to return to anything but the *innermost* catch or block.
>
> -s
>
> On Thu, May 2, 2019 at 2:09 PM andre maute <and...@gm...> wrote:
>
>> So my next logical question would be,
>> if it is possible to extend Maxima
>> with an extra C/C++-like return function?
>>
>> Let's call it 'pt_c_return'.
>>
>> So if I want to prototype something for C++, i would simply use
>> 'pt_c_return' instead of 'return' and be happy.
>>
>> Perhaps a 'pt_c_block' instead of 'block' could be necessary, too.
>>
>> Regards
>> Andre
>>
>> On 5/2/19 1:54 AM, Barton Willis wrote:
>>> -- Function: return (<value>)
>>> May be used to exit explicitly from the current 'block', 'while',
>>> 'for' or 'do' loop bringing its argument. It therefore can be
>>> compared with the 'return' statement found in other programming
>>> languages but it yields one difference: In maxima only returns from
>>> the current block, not from the entire function it was called in.
>>> In this aspect it more closely resembles the 'break' statement from
>>> C.
>>>
>>>
>>> -- Function: catch (<expr_1>, ..., <expr_n>)
>>> Evaluates <expr_1>, ..., <expr_n> one by one; if any leads to the
>>> evaluation of an expression of the form 'throw (arg)', then the
>>> value of the 'catch' is the value of 'throw (arg)', and no further
>>> expressions are evaluated. This "non-local return" thus goes
>>> through any depth of nesting to the nearest enclosing 'catch'. If
>>> there is no 'catch' enclosing a 'throw', an error message is
>>> printed.
>>>
>>>
>>>
>>> --Barton
>>>
>>>
>>> ________________________________
>>> From: andre maute <and...@gm...>
>>> Sent: Wednesday, May 1, 2019 17:55
>>> To: <max...@li...>
>>> Subject: [Maxima-discuss] using return within a for loop within a
>> function
>>>
>>> Hi list,
>>>
>>> this one baffles me most of the times when prototyping
>>> mathematical code in Maxima respectively C++
>>> and converting between the two languages.
>>>
>>> We have the following two snippets, where the
>>> first one outputs "1" and the second outputs "-1"
>>>
>>> Do I miss something here?
>>> I often resort in these situations to
>>> a solution with extra flags in the Maxima code.
>>>
>>> Regards
>>> Andre
>>>
>>>
>>> ---testreturn.mac---
>>> display2d : false;
>>>
>>> my_foo(d1,d2) := block(
>>>
>>> [res:-1,m],
>>>
>>> for m : 1 thru d2 do block(
>>> if (m = d1) then block(
>>> return(res)
>>> )
>>> ),
>>>
>>> return(d1)
>>> );
>>>
>>> print( my_foo(1,10) );
>>>
>>> ---testreturn.mac---
>>>
>>> ---testreturn.cpp---
>>> #include <iostream>
>>>
>>> int foo(int d1, int d2)
>>> {
>>> int res = -1;
>>>
>>> for(int m = 1; m <= d2; m++) {
>>> if(m == d1) {
>>> return(res);
>>> }
>>> }
>>>
>>> return(d1);
>>> }
>>>
>>> int main()
>>> {
>>> std::cout << foo(1,10) << std::endl;
>>> return 0;
>>> }
>>> ---testreturn.cpp---
>>>
>>>
>>> _______________________________________________
>>> Maxima-discuss mailing list
>>> Max...@li...
>>>
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.sourceforge.net_lists_listinfo_maxima-2Ddiscuss&d=DwICAg&c=Cu5g146wZdoqVuKpTNsYHeFX_rg6kWhlkLF8Eft-wwo&r=Ln0CjFotuA7GyhsRS-QpQA&m=Xp5OvovX7IgrRBp8bcUM9MCo7Kne0r4i075VTbsoTls&s=a2Xp_KW3lx6QItxNr4KIsWlSKhgdDXj8TBmwQgkJDxQ&e=
>>> ________________________________
>>> From: andre maute <and...@gm...>
>>> Sent: Wednesday, May 1, 2019 5:55:44 PM
>>> To: <max...@li...>
>>> Subject: [Maxima-discuss] using return within a for loop within a
>> function
>>>
>>> Hi list,
>>>
>>> this one baffles me most of the times when prototyping
>>> mathematical code in Maxima respectively C++
>>> and converting between the two languages.
>>>
>>> We have the following two snippets, where the
>>> first one outputs "1" and the second outputs "-1"
>>>
>>> Do I miss something here?
>>> I often resort in these situations to
>>> a solution with extra flags in the Maxima code.
>>>
>>> Regards
>>> Andre
>>>
>>>
>>> ---testreturn.mac---
>>> display2d : false;
>>>
>>> my_foo(d1,d2) := block(
>>>
>>> [res:-1,m],
>>>
>>> for m : 1 thru d2 do block(
>>> if (m = d1) then block(
>>> return(res)
>>> )
>>> ),
>>>
>>> return(d1)
>>> );
>>>
>>> print( my_foo(1,10) );
>>>
>>> ---testreturn.mac---
>>>
>>> ---testreturn.cpp---
>>> #include <iostream>
>>>
>>> int foo(int d1, int d2)
>>> {
>>> int res = -1;
>>>
>>> for(int m = 1; m <= d2; m++) {
>>> if(m == d1) {
>>> return(res);
>>> }
>>> }
>>>
>>> return(d1);
>>> }
>>>
>>> int main()
>>> {
>>> std::cout << foo(1,10) << std::endl;
>>> return 0;
>>> }
>>> ---testreturn.cpp---
>>>
>>>
>>> _______________________________________________
>>> Maxima-discuss mailing list
>>> Max...@li...
>>>
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.sourceforge.net_lists_listinfo_maxima-2Ddiscuss&d=DwICAg&c=Cu5g146wZdoqVuKpTNsYHeFX_rg6kWhlkLF8Eft-wwo&r=Ln0CjFotuA7GyhsRS-QpQA&m=Xp5OvovX7IgrRBp8bcUM9MCo7Kne0r4i075VTbsoTls&s=a2Xp_KW3lx6QItxNr4KIsWlSKhgdDXj8TBmwQgkJDxQ&e=
>>>
>>
>>
>>
>> _______________________________________________
>> Maxima-discuss mailing list
>> Max...@li...
>> https://lists.sourceforge.net/lists/listinfo/maxima-discuss
>>
>
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