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Task/Binary-digits/Nim/binary-digits.nim

@@ -0,0 +1,24 @@
+proc binDigits(x: BiggestInt, r: int): int =
+  ## Calculates how many digits `x` has when each digit covers `r` bits.
+  result = 1
+  var y = x shr r
+  while y > 0:
+    y = y shr r
+    inc(result)
+
+proc toBin*(x: BiggestInt, len: Natural = 0): string =
+  ## converts `x` into its binary representation. The resulting string is
+  ## always `len` characters long. By default the length is determined
+  ## automatically. No leading ``0b`` prefix is generated.
+  var
+    mask: BiggestInt = 1
+    shift: BiggestInt = 0
+    len = if len == 0: binDigits(x, 1) else: len
+  result = newString(len)
+  for j in countdown(len-1, 0):
+    result[j] = chr(int((x and mask) shr shift) + ord('0'))
+    shift = shift + 1
+    mask = mask shl 1
+
+for i in 0..15:
+  echo toBin(i)