nimforum mirror - mySeq.map(x => x+1)

mora (orginal) [2015-07-18T11:17:50+02:00] view original

Hi,

I'm playing with => from future.nim, and I have a question. These lines are working:

import future

proc takeProcAndCallWith10(f: proc(x: int): int): int =
  result = f(10)

echo takeProcAndCallWith10((x: int) => x+1) # prints 11
echo takeProcAndCallWith10((x) => x+1) # prints 11
echo takeProcAndCallWith10(x => x+1) # prints 11
assert takeProcAndCallWith10(x => x+1) == 11 # Easter egg: gives SIGSEGV, who knows why

I get some warning messages Typeless parameters are deprecated, which is strange, are these forms will disappear?

I can also create my own function without specifying types:

proc myProc[T](x: T): auto =
  x + 1
echo takeProcAndCallWith10(myProc) # prints 11

So my question is: is it possible to make the following lines work?

echo map(@[1,2,3,4,5], (x: int) => x*10) # prints 11
echo map(@[1,2,3,4,5], (x) => x*10) # fails to compile
echo map(@[1,2,3,4,5], x => x*10) # fails to compile
echo map(@[1,2,3,4,5], myProc) # fails to compile

I know that this might require a smarter generic-type-matcher logic.

Motivation:

Let's consider the following two lines:

echo lines.mapIt(it.len)
echo lines.map(line => line.len) # currently fails to compile

I prefer the second one. It's a little bit longer, but I can give a good variable name instead of using it for everything. If the second line was working, that might kill the need for mapIt.

Thanks,: Peter

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1457 :: mySeq.map(x => x+1)