3 files changed, 23 insertions, 3 deletions
diff --git a/lib/pure/rationals.nim b/lib/pure/rationals.nim
index 60d09c71a..7d9241412 100644
--- a/lib/pure/rationals.nim
+++ b/lib/pure/rationals.nim
@@ -18,8 +18,9 @@ type Rational*[T] = object
   ## a rational number, consisting of a numerator and denominator
   num*, den*: T
 
-proc initRational*[T](num, den: T): Rational[T] =
+proc initRational*[T:SomeInteger](num, den: T): Rational[T] =
   ## Create a new rational number.
+  assert(den != 0, "a denominator of zero value is invalid")
   result.num = num
   result.den = den
 
@@ -33,7 +34,7 @@ proc `$`*[T](x: Rational[T]): string =
   ## Turn a rational number into a string.
   result = $x.num & "/" & $x.den
 
-proc toRational*[T](x: T): Rational[T] =
+proc toRational*[T:SomeInteger](x: T): Rational[T] =
   ## Convert some integer `x` to a rational number.
   result.num = x
   result.den = 1
@@ -47,7 +48,7 @@ proc toInt*[T](x: Rational[T]): int =
   ## `x` does not contain an integer value.
   x.num div x.den
 
-proc reduce*[T](x: var Rational[T]) =
+proc reduce*[T:SomeInteger](x: var Rational[T]) =
   ## Reduce rational `x`.
   let common = gcd(x.num, x.den)
   if x.den > 0:
diff --git a/tests/rational/trat_float.nim b/tests/rational/trat_float.nim
new file mode 100644
index 000000000..24797c4a0
--- /dev/null
+++ b/tests/rational/trat_float.nim
@@ -0,0 +1,9 @@
+discard """
+  file: "trat_float.nim"
+  line: "9,19"
+  errormsg: '''type mismatch: got'''
+"""
+import rationals
+var
+  # this fails - no floats as num or den
+  r = initRational(1.0'f, 1.0'f)
diff --git a/tests/rational/trat_init.nim b/tests/rational/trat_init.nim
new file mode 100644
index 000000000..df29ff6e3
--- /dev/null
+++ b/tests/rational/trat_init.nim
@@ -0,0 +1,10 @@
+discard """
+  file: "trat_init.nim"
+  exitcode: "1"
+"""
+import rationals
+var
+  z = Rational[int](num: 0, den: 1)
+  o = initRational(num=1, den=1)
+  a = initRational(1, 2)
+  r = initRational(1, 0)  # this fails - no zero denominator