The Next 700 Programming Languages (1965) [pdf]

Re:The Next 700 Programming Languages (1965) [pdf] by remcob on Monday January 08, 2018 @06:11PM (#16101787)

First example:

  x(x - k a)

  where x = b + 2c

Now imagine ‘+’ and ‘-’ have side-effects, like a log message. What would the output be? ‘+-’, ‘++-’ or ‘+-+’? Certainly not the ‘-+’ order as they appear in the code, which is causally impossible.

The paper restricts to pure functions, where this is not an issue. But it does seem to violate a widely followed implicit rule that lines of code are in strict causal order, with well-defined explicit exceptions for control flow.

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Re:The Next 700 Programming Languages (1965) [pdf] by theoh on Monday January 08, 2018 @06:54PM (#16102132)

I'm not sure "violate" is the right word, given Landin's objectives.

If the where-clause offends you, use a let-clause instead?

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Re:The Next 700 Programming Languages (1965) [pdf] by abiox on Tuesday January 09, 2018 @08:08PM (#16111740)

this already happens: in a variety of languages, x could just be an ordinary function with the body defined below any given usage. here, `where` could be replaced with a standard function definition, and it's `+` would still be textually below the usage's `-`.

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