ML like pattern matching

[Cagdas Ozgenc]

Greetings,
 
How do I emulate the "when" clause in ML for 
pattern matching? In other words when a pattern is matched (from a list of 
patterns of a function) and to enforce additional predicates I use guards, 
but if the guard condition is not satisfied I want Haskell to get back 
to trying the remaining patterns.
 
Thanks
 
 

Re: ML like pattern matching

[Jonas Ritter]

Hi

Cagdas Ozgenc wrote:
Greetings,
 
How do I emulate the "when" clause in ML for pattern matching? In other 
words when a pattern is matched (from a list of patterns of a 
function) and to enforce additional predicates I use guards, but if the 
guard condition is not satisfied I want Haskell to get back to trying 
the remaining patterns.
 
Thanks
Maybe you hav to reorganize the list of patterns or you use
"otherwise" as the last case of your guard conditions to call the 
function with a more general parameters which matches an other pattern.
A litle example would be helpfull.

Jonas

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Re: ML like pattern matching

[Ganesh Sittampalam]

On Fri, 22 Aug 2003 15:49:15 +0300, "Cagdas Ozgenc" <[EMAIL PROTECTED]>
wrote:

>How do I emulate the "when" clause in ML for pattern matching? In other 
>words when a pattern is matched (from a list of patterns of a function) and 
>to enforce additional predicates I use guards, but if the guard condition is 
>not satisfied I want Haskell to get back to trying the remaining patterns.

I may be confused about what you're asking for, but Haskell does this by
default:

foo (Left x) | x>3 = "bar"
foo _ = "splat"

Main> foo (Left 5)
"bar"
Main> foo (Left 1)
"splat"


Ganesh
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Re: ML like pattern matching

[Cagdas Ozgenc]

Thanks.

I was reading some codes in ML, and it was commented this was the case. I
didn't know Haskell had the equivalent behavior. I always thought once the
pattern was matched there is no going back.

>> I may be confused about what you're asking for, but Haskell does
>> this by default:
>>
>> foo (Left x) | x>3 = "bar"
>> foo _ = "splat"
>>
>> Main> foo (Left 5)
>> "bar"
>> Main> foo (Left 1)
>> "splat"


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