Szathmáry László honlapja @ DEIK | Nim2 / Extract data from a formatted string

`scanf()`

`scanf()`
from parse import parse def main(): s = "mul(11,8)" p = parse("mul({a},{b})", s) print(p["a"]) # "11" print(p["b"]) # "8"	import std/strscans let s = "mul(11,8)" var a, b: int if s.scanf("mul($i,$i)", a, b): echo a # 11 ; as int echo b # 8 ; as int var v1, v2: string if s.scanf("mul($+,$+)", v1, v2): echo v1 # "11" ; as string echo v2 # "8" ; as string
This is a 3rd-party library. You can install it with `pip`.	`scanf()` returns true if the operation was successful; false otherwise `$i`: integer `$+`: string whose length is at least 1

The most important constructions (see the docs for a full list):

`$i`	Matches a decimal integer. Uses `parseInt`.
`$f`	Matches a floating-point number. Uses `parseFloat`.
`$c`	Matches a single ASCII character.
`$s`	Skips optional whitespace(s). Matches multiple whitespace characters.
`$$`	Matches a single dollar sign.
`$*`	Matches until the token following the `$*` was found. The match is allowed to be of 0 length.
`$+`	Matches until the token following the `$+` was found. The match must consist of at least one char.

`scanTuple()`

This module has another useful macro called scanTuple(). It's quite similar to C's scanf().

Let's say that we want to read a line from the standard input that contains three integers:

2 3 5

In C, we'd do this:

int a, b, c;
scanf("%d %d %d", &a, &b, &c);

In Nim:

import std/strscans

let (ok, a, b, c) = scanTuple(stdin.readLine, "$i $i $i")
if ok:
echo a
echo b
echo c

It returns a tuple. The tuple starts with a bool which indicates if the scan was successful followed by the requested data. If you're 100% sure that the input is correct, you can swallow the bool value by using the dummy variable underscore ('_').