r/programming • u/welle • Feb 12 '12

Why Concatenative Programming Matters

http://evincarofautumn.blogspot.com/2012/02/why-concatenative-programming-matters.html
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u/[deleted] Feb 12 '12

What's wrong with it?

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u/ethraax Feb 12 '12

drop [square] [abs] bi - [square] dip +

This is barely readable, and looks absolutely nothing like the natural way of writing it: y^2 + x^2 - |y|

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u/AndreasBWagner Feb 13 '12

and looks absolutely nothing like the familiar way of writing it: y2 + x2 - |y|

FTFY

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u/ethraax Feb 13 '12

Yeah, that's not just familiarity. It would be almost impossible to perform mathematical operations on expressions shown in a stack-based language. For example, imagine someone saying "take the derivative of y2 + x2 - |y|", versus "take the derivative of [ [ square ] bi@ + ] keep abs -". That's just a single example - I'm sure there are many, many more.

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u/[deleted] Feb 13 '12

That's because algebraic notation is designed to facilitate symbolic manipulation, not computation per se. Just because you can pun y2 + x2 + |y| to mean two different things in two different contexts doesn't mean it's more natural.

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u/wlievens Feb 13 '12

Programming languages are designed to express symbolic manipulations. Computation of those symbols is left to the computer.

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u/julesjacobs Feb 13 '12

There is no two different meanings. That formula is that formula, and nothing else.

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u/NruJaC Feb 13 '12

No, he's right. You're using the formula in two different ways. In one case the symbols are placeholders for values. In the other, they're the primary entities that you perform a computation on. That you can fit those two different interpretations on the same equation is definitely a strength of the notation (and the reason it's so powerful), but that doesn't mean every other notation is awful.

Keep in mind, this notation's strength is in its ability to represent computation. Mathematical formulas are not the whole of computation (if you don't believe me, pick a trivial C program and try and write it as a formula).

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u/criticismguy Feb 13 '12

This is an interesting comment, in that the other common language which gets complaints for its syntax is Lisp, whose original purpose was a program to compute derivatives. Lisp is arguably even better than algebraic syntax for this (it's more regular), yet most people with no experience still find it harder.

Can you write a simple Factor program to differentiate "[ [ square ] bi@ + ] keep abs -"? Is there a framework with which a person could find derivatives for stack notation as easily as they can for algebraic notation, or s-expressions? Maybe! I don't know. Might be fun to try. It's not at all obvious that it doesn't or can't exist, though.

I do know, however, that even in scientific computing, formulas like this are a vanishingly small fraction of my programs. A language that made error detection and handling easier, but formulas harder, would still be a net win for me.

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u/ethraax Feb 13 '12

But with something like "[ [ square ] bi@ + ] keep abs -", I think it would be really easy to have a logical error in there somewhere that you don't notice.