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Comment by altcognito | Hacker News Reader

Is Python indentation at some level traced back to Cobol?

I would guess not. indentation in python serves a very different purpose to the mandatory indentation as found in early cobol/fortran.

I am not really an expert but here is my best shot at explaining it based on a 5 minute web search.

Cobol/fortran were designed to run off punch cards, specific columns of the punch card were reserved to specific tasks, things like the sequence number, if the line is a comment, continuation lines.

https://en.wikipedia.org/wiki/COBOL#Code_format

https://web.ics.purdue.edu/~cs154/lectures/lecture024.htm

In python the indentation is a sort of enforced code style guide(sort of like go's refusal to let you load unused modules), by making the indentation you would do normally part of the block syntax, all python programs have to have high quality indentation. whether that author wants to or not.

I don't know much about COBOL, but I did code quite a bit in Fortran. In Fortran, the first five columns were for an optional line number, so these would mostly be blank. The sixth column was a flag that indicated that the line was continued from the one before, this allowed for multiline statements, by default a carriage return was a statement terminator. Like you said, all this came from punch cards.

Columns seven through 72 were for your code

Interestingly, punch cards and early terminals in the 80-132 columns range reached the limits of readable line length and early programming languages were obviously pushed to the limits of human comprehension, making the shape of text in old and new programming languages strikingly consistent (e.g. up to 4 or 5 levels of 4 characters of indentation is normal).

I've heard it was from Haskell?

Block structure as indentation was introduced in Landin's ISWIM. I think the first actual implementation was in Turner's SASL (part of the ancestry of Haskell). Note that Haskell doesn't have Python's ":" and it also has an alternative braces and semicolons block syntax.

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