‘Tool’ is a popular metaphor for a programming language but it’s very limited. ‘Rule’ might be a better metaphor. A language defines, quite literally, what you can and can’t do. People who argue for languages with more power are actually arguing for less rules.



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Is this really about “more power?” Or is this about whether a language has one obvious way to do things vs. more than one way to do things? Python is a considerably more powerful language than Java, but I would consider both languages to be firmly in the “It’s a good thing to impose rules on the programmer” camp.It’s true that languages like Ruby permit programmers more freedom. But is it because such languages give programmers the tools to turn boilerplate into abstractions? Or is it because these languages provide multiple programming paradigms and because they have cultures encouraging programmer responsibility?Java and Python are good languages to contrast. Java began with the idea that removing programmer freedom would produce better programs. Java was built by removing features from C++, and the result is a language with little power ( whatever that means ) and little freedom.Python was also built with the philosophy that removing certain programmer freedoms would produce better programs, however Guido has been careful not to reject features simply because programmers might misuse them. Instead, he has been careful to design Python such that there are few features he deems unnecessary. His definition of unnecessary is a feature where there already exists a perfectly serviceable way to do it in Python.Guido has also tried to remove choice in things that don’t matter, like indentation, while growing the language with features that fit within Python’s style and design æsthetic. The result is a language where programs are easy to read, where you do not have little dialects everywhere.Yet, Python programmers rarely chafe that they are constrained from doing what they need to do. Clearly, it is possible to impose rules and to gently guide programmers towards a standard way to express ideas without hobbling them.Haskell is quite possibly the most extremely limiting language in common use: there is one way to do everything, mathematically pure functional programming . You have strong, expressive static typing . Would anyone argue that switching from Java to Haskell is an attempt to deal with fewer rules and fewer restrictions, an attempt to gain more freedom as a programmer? Likewise, the Factor programming language imposes a single, constraining set of rules on the programmer: programmers switching to Factor must relinquish their local variables to gain Factor’s higher-order programming power.Power and freedom are related ideas. So it is easy to see why many languages that provide more power also provide more freedom than hobbled languages. The trouble is that some languages are built as collections of unrelated features smooshed together, just as some programs are hotch potches of checkbox features. Good design in every field accomplishes the “antigravity” trick of accomplishing more with less. With poor design, adding new power requires adding more check boxes, more features, more ways to do things that interact with each other unexpectedly. It is not surprising that some reasonable people resist growing languages that are not designed well, that cannot grow in power without throwing more features on top of the pile.But languages can provide more power while also providing more rules and, paradoxically, less freedom. It’s just that they provide less freedom to do things that are unimportant to the language designer (like fully unconstrained lambdas in Python) or less freedom to do things that make it difficult to reason about a program’s behavior (like dynamic typing or state changes in Haskell). This is accomplished through careful design from the outset, through having a guiding philosophy, and through building on sound foundations.The issue is not that more power equals more freedom, just that more power (whatever that means) equals a certain kind of freedom denied to those who use less powerful languages. It does not mean more freedom overall, it may mean less freedom overall.I conclude that it is possible to argue for and against language “power” quite separately from arguing for and against constraining programmers with rules. “Collection of Rules” is a decent metaphor for programming languages, and some languages have more rules than others. But it is orthogonal to the metaphor of languages as tools and the discussion of to what extent providing programmers with more powerful tools leads to better programs.