Improve compound name linting and idiomatic checks

src/main/resources/org/eolang/lints/names/compound-name.xsl

@@ -9,14 +9,23 @@
   <xsl:import href="/org/eolang/funcs/special-name.xsl"/>
   <xsl:import href="/org/eolang/funcs/escape.xsl"/>
   <xsl:output encoding="UTF-8" method="xml"/>
-  <!--Since developers might decide not to use kebab-case, it’s better to catch all such cases.-->
+  <!--Since developers might decide not to use kebab-case, it's better to catch all such cases.-->
   <xsl:function name="eo:compound" as="xs:boolean">
     <xsl:param name="name"/>
     <xsl:sequence select="contains($name, '-') or contains($name, '_') or matches($name, '[A-Z]')"/>
   </xsl:function>
+  <!--
+    These prefixes are idiomatic in EO standard library:
+    - 'as-' for type conversions (as-bytes, as-i64, as-number, etc.)
+    - 'is-' for boolean predicates (is-empty, is-nan, is-finite, etc.)
+  -->
+  <xsl:function name="eo:idiomatic" as="xs:boolean">
+    <xsl:param name="name"/>
+    <xsl:sequence select="starts-with($name, 'as-') or starts-with($name, 'is-')"/>
+  </xsl:function>
   <xsl:template match="/">
     <defects>
-      <xsl:for-each select="//o[@base and @name and not(eo:special(@name)) and eo:compound(@name)]">
+      <xsl:for-each select="//o[@base and @name and not(eo:special(@name)) and eo:compound(@name) and not(eo:idiomatic(@name))]">
         <defect>
           <xsl:variable name="line" select="eo:lineno(@line)"/>
           <xsl:attribute name="line">

src/main/resources/org/eolang/motives/names/compound-name.md

@@ -4,6 +4,10 @@ All objects that are not formations must have single-word names.
 Compound names indicate that the program context is too large
 and needs to be decomposed.
 
+There are two exceptions for idiomatic prefixes used in EO standard library:
+the `as-` prefix for type conversions (such as `as-bytes`, `as-i64`, `as-number`)
+and the `is-` prefix for boolean predicates (such as `is-empty`, `is-nan`, `is-finite`).
+
 Incorrect:
 
 ```eo

src/test/resources/org/eolang/lints/packs/single/compound-name/allows-idiomatic-as-and-is-prefixes.yaml

@@ -0,0 +1,14 @@
+# SPDX-FileCopyrightText: Copyright (c) 2016-2026 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/names/compound-name.xsl
+asserts:
+  - /defects[count(defect[@severity='warning'])=0]
+input: |
+  # No comments.
+  [] > main
+    x.as-bytes > as-bytes
+    y.as-i64 > as-i64
+    z.is-empty > is-empty
+    w.is-nan > is-nan