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I'm surprised that you draw a sharp distinction between C and Pascal syntax. They have a shared lineage and are really very close to each other. Yeah, curly braces won over "begin" and "end", but that's not a matter of some huge conceptual rift, just convenience. There are numerous languages today, including Haskell and Ocaml, that are far more removed from the Algol lineage than these two. Heck, the differences betw…
One huge difference between C and Pascal grammars us that Pascal is LR(1), so it can be parsed easily, which helps one-pass translation. It also helps humans read it. C, on the other hand, has needlessly complicated syntax; a function definition is hard to detect, and a pointer to a function is hard to interpret, because it's literally convoluted: https://c-faq.com/decl/spiral.anderson.html Sadly, this is a general s…
C is almost LR(1), if we allow prior declarations to decide how some tokens are classified, like whether an identifier is a variable or type name.
Declarations like
void (*signal(int, void (*fp)(int)))(int);
LR(1) sentences are harder to read than LL(1) because you have to keep track of a long prefix of the input, looking for right reductions (if you follow certain LR algorithms). LR parsing algorithms use a stack which essentially provides unlimited lookahead, in comparison to LL(1). Both LL(1) and LR(1) have one symbol of lookahead, but qualitatively it's entirely different because the lookahead in LR is happening after an indefinitely long prefix of the sentence which has not been fully analyzed, and has been shunted into a stack, to be processed later. Many symbols can be pushed onto the stack before a decision is made to recognize a rule and reduce by it. Those pushed symbols represent a prefix of the input that is not yet reduced, while the reduction is happening on the right of that. So it is backwards in a sense; following what is going on in the grammar is bit like understanding a stack language like Forth or PostScript.
An LL(1) grammar allows sentences to be parsed in a left to right scan without pushing anything into a stack to reduce later. Everything is decidable based on looking at the next symbol. Under LL(1), by looking at one symbol, you know what you are parsing; each subsequent symbol narrows it down to something more specific. Importantly, the syntax of symbols that have been processed already (material to the left) are settled; their syntax is not left undecided while we recognize some fragment on the right.
Under LR(1) it's possible for a long sequence of symbols to belong to entirely unrelated phrase structures, only to be decided when something finally appears on the right. A LALR(1) parser generator outputs a machine in which the states end up shared by unrelated rules. The state transitions then effectively track multiple parallel contexts.