feat(num): add is_num func

Author: kollhof

src/num.fnk

@@ -1,3 +1,7 @@
+{parseFloat, parseInt, Number, isNaN, isFinite} = import '@fink/js-interop/globals'
+{is_instance, get_type} = import '@fink/js-interop/reflect'
+
+
 # TODO: should that live in str?
 parse_float = fn str: parseFloat str
 
@@ -19,3 +23,10 @@ is_not_a_num = isNaN
 is_finite = isFinite
 
 base_n = fn num, radix: num.toString radix
+
+
+is_num = fn num:
+  match num:
+    'number' == get_type ?: true
+    is_instance ?, Number: true
+    else: false

src/num.test.fnk

@@ -1,6 +1,8 @@
 {describe, it, expect, to_equal} = import '@fink/jest'
+{new} = import '@fink/js-interop/reflect'
+{Number} = import '@fink/js-interop/globals'
 
-{parse_int, parse_float, base_n} = import './num'
+{parse_int, parse_float, base_n, is_num} = import './num'
 
 
 describe 'numbers', fn:
@@ -38,3 +40,20 @@ describe 'numbers', fn:
       base_n 1234, 36
       to_equal
         'ya'
+
+
+
+describe 'is_num', fn:
+  it 'is a number', fn:
+    expect
+      is_num 1234
+      to_equal true
+
+    expect
+      is_num new Number, 1234
+      to_equal true
+
+  it 'is not a number', fn:
+    expect
+      is_num '1234'
+      to_equal false