[clean-list] safe arithmetic operations

[Scott J.]

Thanks this is what I wanted

Thx

Scott


----- Original Message -----
From: "John van Groningen" <johnvg@cs.kun.nl>
To: "Scott J." <jscott@skynet.be>
Cc: <clean-list@jay.skynet.be>
Sent: Wednesday, November 13, 2002 4:23 PM
Subject: Re: [clean-list] safe arithmetic operations


>
> Scott wrote:
> >My wish list is : make the operations + and * truly safe.
>
> I assume that with safe you mean that arithmetic overflows are detected.
> This would break some existing programs and it would make programs slower.
>
> I have implemented a module 'SafeInt' with +, - and * that detect
overflows.
> The code is included in this mesage (at the end). Compile this module
first
> before using it, because otherwise inlining will not work the first time.
>
> >Clean should make a distinction between finite lists and infinite lists.
But I think this is more difficult  than my above wish.
>
> Tail strict lists have already been implemented. It is probably possible
to
> prevent cycles in lists, but we currently don't plan to implement this.
>
> Regards,
>
> John van Groningen
>
>
> implementation module SafeInt;
>
> import StdMisc;
>
> (+%) infixl 6 :: !Int !Int -> Int;
> (+%) a b = code {
> .inline +%
> .newlocallabel l
> addIo
> jmp_false l
> jmp e_SafeInt_sadd_overflow
> :l
> .end
> }
>
> (-%) infixl 6 :: !Int !Int -> Int;
> (-%) a b = code {
> .inline -%
> .newlocallabel l
> subIo
> jmp_false l
> jmp e_SafeInt_ssub_overflow
> :l
> .end
> }
>
> (*%) infixl 6 :: !Int !Int -> Int;
> (*%) a b = code {
> .inline *%
> .newlocallabel l
> mulIo
> jmp_false l
> jmp e_SafeInt_smul_overflow
> :l
> .end
> }
>
> add_overflow :: .a;
> add_overflow = abort "+% overflow";
>
> sub_overflow :: .a;
> sub_overflow = abort "-% overflow";
>
> mul_overflow :: .a;
> mul_overflow = abort "*% overflow";
>
>
> system module SafeInt;
>
> (+%) infixl 6 :: !Int !Int -> Int;
> (-%) infixl 6 :: !Int !Int -> Int;
> (*%) infixl 6 :: !Int !Int -> Int;
>
> add_overflow :: .a;
> sub_overflow :: .a;
> mul_overflow :: .a;
>
>
>
>
>
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