docs/howto: validate an integer value's parity

This adds a Commented Cue guide demonstrating how to validate an integer
value's parity.

Examples are provided for the 8 different validation outcomes, based on
the following matrix:
- odd/even
- positive/negative
- valid/invalid

For cue-lang/docs-and-content#97

Preview-Path: /docs/howto/validate-integer-value-parity/
Change-Id: Ibc7a31dcbbb13a8d155f30731c961691e47d79ed
Signed-off-by: Noam Dolovich <noam.tzvi.dolovich@gmail.com>
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cuelang.org/+/1177968
Reviewed-by: Paul Jolly <paul@myitcv.io>
Reviewed-by: Jonathan Matthews <github@hello.jonathanmatthews.com>
TryBot-Result: CUEcueckoo <cueckoo@gmail.com>

content/authors/noamtd/en.md

@@ -0,0 +1,3 @@
+---
+displayName: "Noam Dolovich"
+---

content/authors/noamtd/page.cue

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+package site
+
+content: authors: noamtd: page: _

content/docs/howto/validate-integer-value-parity/en.md

@@ -0,0 +1,55 @@
+---
+title: Validating an integer value's parity
+tags:
+- commented cue
+- validation
+authors:
+- noamtd
+toc_hide: true
+---
+
+This [Commented CUE]({{< relref "docs/howto#commented-cue-guides" >}})
+demonstrates how to validate an integer value's parity.
+
+Two schemas `#Odd` and `#Even` are presented that validate an integer is either odd or even respectively.
+
+{{{with code "en" "cc"}}}
+exec cue eval -ic
+cmp stdout out
+-- file.cue --
+package example
+
+#Even: num={2 * (div(num, 2))}
+#Odd:  num={1 + 2*(div(num, 2))}
+
+valid: {
+	"-27": -27 & #Odd
+	"-22": -22 & #Even
+	"42":  42 & #Even
+	"47":  47 & #Odd
+}
+
+invalid: {
+	"-37": -37 & #Even
+	"-32": -32 & #Odd
+	"52":  52 & #Odd
+	"57":  57 & #Even
+}
+-- out --
+valid: {
+    "-27": -27
+    "-22": -22
+    "42":  42
+    "47":  47
+}
+invalid: {
+    "-37": _|_ // invalid."-37": conflicting values -38 and -37
+    "-32": _|_ // invalid."-32": conflicting values -31 and -32
+    "52":  _|_ // invalid."52": conflicting values 53 and 52
+    "57":  _|_ // invalid."57": conflicting values 56 and 57
+}
+{{{end}}}
+
+## Related content
+
+* {{< linkto/related/howto "use-the-built-in-functions-div-mod-quo-rem" >}}

content/docs/howto/validate-integer-value-parity/gen_cache.cue

@@ -0,0 +1,18 @@
+package site
+{
+	content: {
+		docs: {
+			howto: {
+				"validate-integer-value-parity": {
+					page: {
+						cache: {
+							code: {
+								cc: "vf+j3IRvnHFecRWPM2a/7OODOwIDnMF6Rv3dTjzKZns="
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+}

content/docs/howto/validate-integer-value-parity/page.cue

@@ -0,0 +1,3 @@
+package site
+
+content: docs: howto: "validate-integer-value-parity": page: _

hugo/content/en/authors/noamtd/index.md

@@ -0,0 +1,3 @@
+---
+displayName: "Noam Dolovich"
+---

hugo/content/en/docs/howto/validate-integer-value-parity/index.md

@@ -0,0 +1,56 @@
+---
+title: Validating an integer value's parity
+tags:
+- commented cue
+- validation
+authors:
+- noamtd
+toc_hide: true
+---
+
+This [Commented CUE]({{< relref "docs/howto#commented-cue-guides" >}})
+demonstrates how to validate an integer value's parity.
+
+Two schemas `#Odd` and `#Even` are presented that validate an integer is either odd or even respectively.
+
+{{< code-tabs >}}
+{{< code-tab name="file.cue" language="cue" area="top-left" >}}
+package example
+
+#Even: num={2 * (div(num, 2))}
+#Odd:  num={1 + 2*(div(num, 2))}
+
+valid: {
+	"-27": -27 & #Odd
+	"-22": -22 & #Even
+	"42":  42 & #Even
+	"47":  47 & #Odd
+}
+
+invalid: {
+	"-37": -37 & #Even
+	"-32": -32 & #Odd
+	"52":  52 & #Odd
+	"57":  57 & #Even
+}
+{{< /code-tab >}}
+{{< code-tab name="TERMINAL" language="" area="top-right" type="terminal" codetocopy="Y3VlIGV2YWwgLWlj" >}}
+$ cue eval -ic
+valid: {
+    "-27": -27
+    "-22": -22
+    "42":  42
+    "47":  47
+}
+invalid: {
+    "-37": _|_ // invalid."-37": conflicting values -38 and -37
+    "-32": _|_ // invalid."-32": conflicting values -31 and -32
+    "52":  _|_ // invalid."52": conflicting values 53 and 52
+    "57":  _|_ // invalid."57": conflicting values 56 and 57
+}
+{{< /code-tab >}}
+{{< /code-tabs >}}
+
+## Related content
+
+* {{< linkto/related/howto "use-the-built-in-functions-div-mod-quo-rem" >}}