Re^4: Strong typing and Type Safety.A multilanguage approach

http://www.perlmonks.org?node_id=872653

in reply to Re^3: Strong typing and Type Safety.A multilanguage approach
in thread Strong typing and Type Safety.A multilanguage approach

that using the numeric + operator on a Perl string is "implicit" and therefore weakly typed

no but the conversion from string to number is

Comment on Re^4: Strong typing and Type Safety.A multilanguage approach

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Re^5: Strong typing and Type Safety.A multilanguage approach by eyepopslikeamosquito (Archbishop) on Nov 20, 2010 at 10:47 UTC
No. By using the `+` operator, you are explicitly asking for the string to be converted to a number. Why do you say it is implicit? (This thread may be heading towards Room 12A).	[reply] [d/l]
Re^6: Strong typing and Type Safety.A multilanguage approach (implicit) by tye (Sage) on Nov 20, 2010 at 21:09 UTC
Sure, I can "explicitly" do `0+` with the intent of converting a string into a number. "Explicit" describes my motivation. But, no, `1+$duration` is not an explicit type conversion, it is explicit addition that implies a type conversion, if required. I can write `1+$duration` with no intention of doing a conversion. If I am mistaken in thinking that $duration holds a numeric value and write `1+$duration`, since the explicit request for addition includes in it an implicit possibility of type conversion, the compiler can't tell that I didn't mean for a conversion to happen. The type conversion is called "implicit". Having to write `1+(int)$duration` is much more explicit. Type conversion is only done when I explicitly say "do a type conversion" not when I say "do addition" and can't separately specify that I want a conversion. - tye	[reply] [d/l] [select]
Re^7: Strong typing and Type Safety.A multilanguage approach (implicit) by chromatic (Archbishop) on Nov 22, 2010 at 00:12 UTC
`1+$duration` is not an explicit type conversion, it is explicit addition that implies a type conversion, if required. `+` is a monomorphic operator. So is `.`. Perl values are polymorphic. Arguing that operator-enforced coercions in Perl are implicit is silly nonsense; to do so you must assume a priori that values should be monomorphic. I can write `1+$duration` with no intention of doing a conversion. You can also write `$string + $duration` with no intention of performing addition, but that has nothing to do with typing and everything to do with you writing buggy (or poorly understood) code.	[reply] [d/l] [select]
Re^8: Strong typing and Type Safety.A multilanguage approach (implicit) by ikegami (Patriarch) on Nov 22, 2010 at 01:59 UTC
Re^9: Strong typing and Type Safety.A multilanguage approach (implicit) by chromatic (Archbishop) on Nov 22, 2010 at 02:23 UTC
Some notes below your chosen depth have not been shown here
Re^6: Strong typing and Type Safety.A multilanguage approach by nikosv (Deacon) on Nov 20, 2010 at 15:40 UTC
Quoting Modern Perl Books page 15 Perl will do its best to coerce values to the proper type (see Coercion, page 47), depending on the operators you use. Be sure to use the proper operator for the type of context you want. Quoting Wikipedia Type Conversion In most languages, the word coercion* is used to denote an implicit conversion, either during compilation or during run time.*	[reply]
Re^7: Strong typing and Type Safety.A multilanguage approach by chromatic (Archbishop) on Nov 20, 2010 at 18:12 UTC
Allow me to assure you that the author of Modern Perl disagrees with your interpretation of his words.	[reply]

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