add isStringNumeric to library

ascii.libsonnet

@@ -26,4 +26,10 @@ local d = import 'github.com/jsonnet-libs/docsonnet/doc-util/main.libsonnet';
     [d.arg('c', d.T.string)]
   ),
   isNumber(c): std.isNumber(c) || (cp(c) >= 48 && cp(c) < 58),
+
+  '#isStringNumeric':: d.fn(
+    '`isStringNumeric` reports whether string `s` consists only of numeric characters.',
+    [d.arg('str', d.T.string)]
+  ),
+  isStringNumeric(str): std.all(std.map(self.isNumber, std.stringChars(str))),
 }

docs/ascii.md

@@ -14,6 +14,7 @@ local ascii = import "github.com/jsonnet-libs/xtd/ascii.libsonnet"
 
 * [`fn isLower(c)`](#fn-islower)
 * [`fn isNumber(c)`](#fn-isnumber)
+* [`fn isStringNumeric(str)`](#fn-isstringnumeric)
 * [`fn isUpper(c)`](#fn-isupper)
 
 ## Fields
@@ -34,6 +35,14 @@ isNumber(c)
 
 `isNumber` reports whether character `c` is a number.
 
+### fn isStringNumeric
+
+```ts
+isStringNumeric(str)
+```
+
+`isStringNumeric` reports whether string `s` consists only of numeric characters.
+
 ### fn isUpper
 
 ```ts

test/ascii_test.jsonnet

@@ -0,0 +1,44 @@
+local ascii = import '../ascii.libsonnet';
+local test = import 'github.com/jsonnet-libs/testonnet/main.libsonnet';
+
+test.new(std.thisFile)
+
++ test.case.new(
+  name='all numeric',
+  test=test.expect.eq(
+    actual=ascii.isStringNumeric('123'),
+    expected=true,
+  )
+)
+
++ test.case.new(
+  name='only beginning numeric',
+  test=test.expect.eq(
+    actual=ascii.isStringNumeric('123abc'),
+    expected=false,
+  )
+)
+
++ test.case.new(
+  name='only end numeric',
+  test=test.expect.eq(
+    actual=ascii.isStringNumeric('abc123'),
+    expected=false,
+  )
+)
+
++ test.case.new(
+  name='none numeric',
+  test=test.expect.eq(
+    actual=ascii.isStringNumeric('abc'),
+    expected=false,
+  )
+)
+
++ test.case.new(
+  name='empty',
+  test=test.expect.eq(
+    actual=ascii.isStringNumeric(''),
+    expected=true,
+  )
+)