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POSeeking clarification on apparent contradictions regarding weakly typed languages
 

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  1. POSeeking clarification on apparent contradictions regarding weakly typed languages
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    <p>I think I understand <a href="http://lucacardelli.name/Papers/OnUnderstanding.A4.pdf" rel="noreferrer">strong typing</a>, but every time I look for examples for what is weak typing I end up finding examples of programming languages that simply coerce/convert types automatically.</p> <p>For instance, in this article named <a href="http://www.artima.com/weblogs/viewpost.jsp?thread=7590" rel="noreferrer">Typing: Strong vs. Weak, Static vs. Dynamic</a> says that Python is strongly typed because you get an exception if you try to:</p> <p><strong>Python</strong></p> <pre><code>1 + "1" Traceback (most recent call last): File "", line 1, in ? TypeError: unsupported operand type(s) for +: 'int' and 'str' </code></pre> <p>However, such thing is possible in Java and in C#, and we do not consider them weakly typed just for that.</p> <p><strong>Java</strong></p> <pre><code> int a = 10; String b = "b"; String result = a + b; System.out.println(result); </code></pre> <p><strong>C#</strong></p> <pre><code>int a = 10; string b = "b"; string c = a + b; Console.WriteLine(c); </code></pre> <p>In this another article named <a href="http://www.i-programmer.info/programming/theory/1469-type-systems-demystified-part2-weak-vs-strong.html" rel="noreferrer">Weakly Type Languages</a> the author says that Perl is weakly typed simply because I can concatenate a string to a number and viceversa without any explicit conversion.</p> <p><strong>Perl</strong></p> <pre><code>$a=10; $b="a"; $c=$a.$b; print $c; #10a </code></pre> <p>So the same example makes Perl weakly typed, but not Java and C#?.</p> <p>Gee, this is confusing <img src="https://i.stack.imgur.com/U5kPT.gif" alt="enter image description here"></p> <p>The authors seem to imply that a language that prevents the application of certain operations on values of different types is strongly typed and the contrary means weakly typed.</p> <p>Therefore, at some point I have felt prompted to believe that if a language provides a lot of automatic conversions or coercion between types (as perl) may end up being considered weakly typed, whereas other languages that provide only a few conversions may end up being considered strongly typed. </p> <p>I am inclined to believe, though, that I must be wrong in this interepretation, I just do not know why or how to explain it.</p> <p>So, my questions are: </p> <ul> <li>What does it really mean for a language to be truly weakly typed? </li> <li>Could you mention any good examples of weakly typing that are not related to automatic conversion/automatic coercion done by the language?</li> <li>Can a language be weakly typed and strongly typed at the same time?</li> </ul>
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    1. USEdwin Dalorzo
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    1. COThis baffles me too! As far as I understand (or think to understand), weakly typed language are said to be 'type safe' and they have implicit type conversion.
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    2. COStrong versus weak typing is all about type conversion (what else could it be about?) If you want an example of a "very" weak language, watch this: https://www.destroyallsoftware.com/talks/wat.
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    3. CO@Wildduck All languages provide type conversions, but not all of them are considered weakly typed. My examples shown below demonstrate how programmers consider a language weakly typed based on the same examples that are possible on other languages considered strongly typed. As such my question still prevails. What is the difference?
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