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10569 :: how to wrap c scanf procedure in nim

• isaiah (orginal) [2023-10-27T22:24:36+02:00] view original

  i been able to wrap printf, sqrt from math.h. but finding it difficult to wrap scanf.i will appreciate any help.

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• PMunch (orginal) [2023-10-27T23:19:20+02:00] view original

  You will have to be more specific. What isn't working, what have you tried, etc.? It should be the same signature as a printf, so something like this should work:

  proc scanf(formatstr: cstring) {.importc: "scanf", varargs, header: "<stdio.h>".}
  Run

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• cblake (orginal) [2023-10-28T01:32:06+02:00] view original

  Maybe being explicit here will help. So,

  proc scanf*(fmt: cstring): int {.importc, varargs.}
  var a, b, c: cint
  echo scanf("%d %d %d", a.addr, b.addr, c.addr) # 3
  echo a # first 3 cints that
  echo b # user put into stdin
  echo c
  Run

  Save the above in a file called scan.nim. Then

  
  echo 1 2 3 | nim r scan
  Run

  produces four lines ("3\n1\n2\n3\n") while

  
  echo a b c | nim r scan
  Run

  produces four lines of zeros ("0\n0\n0\n0\n") since "a" etc. do not parse as decimal integers and since Nim inits them to zero by default (unless you tag the names with the {.noInit.} pragma or give them some other default).

  This said, you should also know that the Nim std lib has std/strscans which is nicer in many ways except for porting legacy input parsing: https://nim-lang.org/docs/strscans.html

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• isaiah (orginal) [2023-10-28T03:43:23+02:00] view original

  thanks it worked well.i am interested in building something usefull with nim.please could you make a suggestion. something not too hard and too easy.

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• janAkali (orginal) [2023-10-28T05:27:57+02:00] view original

  I am interested in building something useful with nim, please could you make a suggestion.

  The best option is to find something that bothers you in your daily routine. And try to fix, improve or to automate it.

  If you're still unsure, you can pick one of problems from public lists:

  • https://github.com/karan/Projects

  Also, Python folks often recommend free books by Al Sweigart: https://inventwithpython.com/

  While it's mostly tutorials for Python, they also have cool little projects you can build either with nimpy or in pure Nim. In particular, look at the "Big book of small Python projects" - https://inventwithpython.com/#bigbookpython

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