Nitpicking on example in chapter 8

[eevman]

In "My First Functor", there is this example:

Container.of('bombs').map(concat(' away')).map(prop('length')); 
// Container(10)

Assuming that concat is defined as in appendix C:

const concat = curry((a, b) => a.concat(b));

Container.of('bombs').map(concat(' away'))
gives the result

Container(' awaybombs')

and not

Container('bombs away')

which I suppose was the intended meaning...
Of course both give the final answer 10 :-)
Shouldn't the example be:

Container.of('bombs').map(append(' away')).map(prop('length')); 
// Container(10)

where append is:

const append = flip(concat);

or something similar?
Or is maybe concat defined as

const concat = curry((a, b) => b.concat(a));

but then it would be difficult to know what function concat does without looking at the implementation...
Any thoughts on this?

[eevman]

Later in the chapter there is:

Either.of('rain').map(str => `b${str}`);

Maybe here we could use the same pattern:

Container.of('bombs').map(str => `${str} away`).map(prop('length'));

[KtorZ]

Indeed, this was already reported by someone not so long ago. We should definitely have an append function here :)

[eevman]

A followup question: shouldn't we add append to Appendix C? It is only mentioned in example in Chapter 5

I have found the report.

[eevman]

Further on in chapter 8, there's this strange example:

const compLaw1 = compose(map(concat(' world')), map(concat(' cruel')));
const compLaw2 = map(compose(concat(' world'), concat(' cruel')));

compLaw1(Container.of('Goodbye')); // Container(' world cruelGoodbye')
compLaw2(Container.of('Goodbye')); // Container(' world cruelGoodbye')

This was changed in #191. I wonder why didn't they use append instead of changing the output to be correct in a strange way? :-)

[eevman]

In chapter 9, there are two problematic uses of concat:

IO.of('tetris').map(concat(' master'));
// IO('tetris master')

Either.of('The past, present and future walk into a bar...').map(concat('it was tense.'));
// Right('The past, present and future walk into a bar...it was tense.')