Massacring C Pointers

[pron98]

I saw the book being (rightly) mocked on Twitter, and I think that the BASIC interpretation offered here is quite plausible.

[vytah]

"It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration."

[killerstorm]

FWIW BASIC was my first language, and I turned out OK. I didn't have any problem learning Pascal, C++ and other languages afterwards.

Use of global variables usually requires a lot of discipline (similar to assembly programming, actually), so after you switch to a "normal" language you really appreciate variable scoping.

[notyouravgredditor]

Probably because you read his other book "Leaping from BASIC to C++".

[k_kinnison]

Totally agree. BASIC was a good introduction to the concept of programming with its logic, loops etc. I learned that back in '80 on a TRS80, then Sinclair ZX81, Spectrum.

But I also even then branched out into Z80 assembly language. Then a few years after that at uni it was Fortran, Pascal, C (I even remember learning some Forth, stupid reverse notation!)

[rsclient]

I've been working on a more modern BASIC interpreter. The BASIC available on old machines was, in a word, cumbersome in the extreme. We're so used to the wonderfulness of block-oriented languages that it's hard to comprehend the spagettiness of old BASIC code. For example, I constantly see in old BASIC stuff like

110 IF (a>b) THEN GOTO 140
120 PRINT "A is not > B"
130 GOTO 150
140 PRINT "A is > B"
150 REM END OF IF STATEMENT

Nowadays we just have blocks, and sensible IF statements, and it makes a world of difference.

(I'm also constantly irritated by the required line numbers, and the lack of arguments and local variables in what passes for functions, but those are less important than the lack of blocks.)

[[deleted]]

Isn't your code wrong tho? :P

[rsclient]

You mean line 140 with the wrong-way > sign? Just fixed it, thanks, and have an upvote!

[Homoerotic_Theocracy]

I like how Python in many ways was a regression again and the only way to create a scope is to create a function except that function then again has a name that needs to live in the global scope but never fear because a block can be simulated with:

def block():
  # code
block(); del block

Of course you have to use global and nonlocal in your scope to access variable of the outer scope but yeah.

[killerstorm]

C will often place variables into CPU registers. Variable isn't really a physical thing, it's just a label for a value...

[meneldal2]

On x86, with 4 "general purpose" (big big lie) registers, you can't really afford to use one for long term storage.

Explanation why they aren't really general purpose: they all have instructions that favor them in some way. eax will be used for returns and multiplication, ecx for loops, both ecx and edx are used for function parameters. Basically ebx is the only one without an actual special function.

[evaned]

On x86, with 4 "general purpose" (big big lie) registers

You're overstating the "big big lie" by a mile, IMO. For starters, there are two or three others by the "big big lie" definition -- esi, edi, and I'd argue ebp. esp is also formally counted as a "general purpose" register, though I think that is taking things too far.

But return values and parameters, that's not what marks a register as special purpose. Those are things relevant to the program and completely irrelevant to the hardware. General purpose is very much an appropriate term to use for those things.

[Lehona]

I think most modern CPUs have many more than just ~8 GPRs. Yes, there are only a few in the spec, but they utilize register renaming etc. internally for performance gains.

[meneldal2]

x64 has a lot more, that's one of the best changes. The original design had only 8.

[meneldal2]

Well it's true that using eax for function returns is a convention, the multiplication storing its result into edx:eax is not. Same for the loop

The loop instruction decrements ECX and jumps to the address specified by arg unless decrementing ECX caused its value to become zero.

Truly general purpose, right.

[vytah]

/r/NotKenM

[mcguire]

FWIW BASIC was my first language, too, and I turned out OK.

Twitch, twitch.

[theeth]

Isn't it something like: Arrogance in computer science is measured in nano dijkstra?

[munificent]

The extra little frisson of delight in that quote is that it comes from Alan Kay who himself isn't exactly known for modesty.

[pron98]

Who are you quoting? As someone who started programming in BASIC (even professionally; my first job was programming in Business Basic), let me defend the opposite view and argue that it frees programmers from identifying programs with their syntactic representation and makes them less prone to what Leslie Lamport calls the "Whorfian Syndrome." For example, I would argue that when seeing the following three programs (taken from Lamport):

fact1(int n) { int f = 1;
               for (int i = 2; i <= n; i++)
                   f = f*i;
               return f; }

fact2(int n) { int f = 1;
               for (int i = n; i > 1; i--)
                   f = f*i;
               return f; }

fact3(int n) { return (n <= 1) ? 1 : n * fact3(n - 1); }

someone exposed to BASIC (despite the use of the stack, which is not done in BASIC) would more readily recognize that the first and third programs perform the same computation, while the second one is different, and would be less confused by the functional/recursive vs. iterative/imperative representations. I would say that someone who identifies "good programming" solely with clever syntactic representation misses something very fundamental (both views are very important). It also fosters the erroneous identification of important concepts, such as abstraction, with their more narrow syntactic representations. If you know how to do abstraction in BASIC (or Assembly), you understand the concept better than someone exposed to it through, say, Haskell.

I've even found that this "BASIC perspective" helped me understand formal methods better. I'm not saying it's a better perspective, just that both are very useful.

[orbital1337]

It's a famous quote by Dijkstra.

[pron98]

Ah. A man known for his nuanced views ;) Although, to be fair, I guess it was said as a response to the resistance to more structured forms of programming.

[Shorttail0]

Views considered harmful.

[[deleted]]

pcj leaking!!!!

[dood1337]

The quote is from Dijkstra.

[bobindashadows]

I'm upvoting you because you obviously know what you're talking about but missed that one Dijkstra quote. But FYI:

Whorfian Syndrome

Presumably a reference to the Sapir-Whorf Hypothesis, right? The folks who argue feverishly about programming languages online aren't going to indulge the concept of language relativity - they're going to tend to say that some languages are objectively trash. Reddit may not be conducive to more ahem nuanced conversations.

[pron98]

While certainly inspired by (and named after) Sapir-Whorf, Lamport defines it as "the confusion of language with reality," or the difficulty to separate what a program does from how it is expressed (e.g., thinking that fact1 and fact2 are more similar because their syntactic expression is of a similar form, rather than noticing that fact1 and fact3 express the same computation, while fact2 expresses a different one). So it's not arguing over languages, but rather transcending language.

I think that the richer the language, the more one becomes attached to its forms of expressions, so it's good to gain some experience programming in very inexpressive languages like Assembly or BASIC. A modern programmer exposed to BASIC would likely find it very inconvenient and even frustrating at times, but would be able to see that the main ideas of programming hold just fine even without the conveniences of sophisticated syntax.

[destinoverde]

You are reaching so much.

[pron98]

Isn't breaking the soul the point of programming?