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Comment by ghewgill | Hacker News Reader

One of the problems with the old notation is the ambiguity. What does each of the following mean?

    n =- 5
    n = -5
    n=-5

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Dennis Ritchie, in his paper about the history of C, explains that they became aware of these ambiguities only after the first C implementation, but they considered that it was a too big mistake, so they reversed the order in the next C version.

maybe not quite the next version, from memory (and I ported compilers, and the kernels, for both) it was between v6 and v7 Unix

That's correct, it wasn't the next version of the Ritchie compiler, it was a whole new compiler, the Portable C Compiler. It used yacc to generate the parser, and yacc complained about the ambiguity. They left the old syntax in for quite a while.

Yup, almost certainly PCC - which also still has struct fields in a global namespace as a (possible wonderful, possibly horrible) hack to provide the equivalent to unions

If I were designing a new language and where dead-set on the =- form I would make it so:

    n =- 5 // n equals n - 5
    n = -5 // n equals -5
    n=-5   //Illegal

This can be done, it just requires getting the lexer right.

Another problem:

n =* p;

Is p a pointer or an integer? Maybe you want to do pointer math, it's a very C thing to do.

That was my thought too - seems like it would be ambiguous even with type information anyway as the readme says this iteration at least, any type can be converted to any other type.

The modern notation contains a very similar 'ambiguity'. Compare: x---y, x-- - y, and x - --y.

And sadly x-----y won't parse :(

It's been a while I used C, but I for one am kind of glad that doesn't parse. If you need to do this, you can use parentheses:

    x - (--y)

    (x--) - y

All parse fine, and unambiguously, due to the maximal munch rule.

x---y is (x--)-y, which is semantically valid.

x-----y is ((x--)--)-y - but it's a semantic error, as x-- is not an lvalue.

Ahh yes, that’s a very good point.

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