Documentation change: Now showing the difference between map and and_then with an example.

[sandeep-datta]

Updated documentation to clarify the difference between and_then and map. This also explains why we need and_then in addition to map. Please look at the diff for more information.

r? @alexcrichton

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[alexcrichton]

Thanks! Could you also wrap the lines to 80 chars (appears to be the surrounding style). For the actual content, though:

r? @steveklabnik

[sandeep-datta]

I just felt the manually inserted 80 char wide line breaks are an anachronism in this day and age. Almost all editors can do word wrapping now. The reader should be given a choice of where they want to see the line breaks instead of making this decision for them. IMO line breaks should only be used to delineate paragraphs.

Also I think unnecessary hard line breaks will make whitespace significant during file merge/comparison and make it unnecessarily hard to contribute. For example you might overflow the 80 char limit when adding a word to a line and end up with a cascading change which affects multiple lines thus making it difficult to see what was actually changed. There may be other complications arising out of this decision.

I vote for removing hard line breaks from the document altogether. But I do not want to upset the apple cart on the other hand so please let me know if you would like to go with ...

1. Removing hard line breaks from the whole document or...
2. Uniformly breaking lines at the 80 char limit (for my changes only).

[alexcrichton]

Er sorry but this is just the style we use, changing it isn't really within the scope of this PR.

[sandeep-datta]

@alexcrichton, changed to 80 char column now.

[steveklabnik]

@bors: r+ rollup

Thank you!

[bors]

📌 Commit 5f20143 has been approved by steveklabnik

[bors]

⌛ Testing commit 5f20143 with merge 1998e3a...

[bors]

💔 Test failed - auto-mac-64-nopt-t

[steveklabnik]

this needs to be marked ignore as well, so that it doesn't get tested.

[steveklabnik]

@bors: r-

[sandeep-datta]

@steveklabnik please review and commit.

[steveklabnik]

@bors: r+ rollup

thank you!

[bors]

📌 Commit 0922d7e has been approved by steveklabnik