Sprintf realization

eo-runtime/pom.xml

@@ -168,6 +168,12 @@
       <version>2.1.6</version>
       <scope>test</scope>
     </dependency>
+
+    <dependency>
+      <groupId>org.eolang</groupId>
+      <artifactId>eo-strings</artifactId>
+      <version>0.1.1</version>
+    </dependency>
   </dependencies>
   <build>
     <plugins>

eo-runtime/src/main/eo/org/eolang/io/sprintf.eo

@@ -0,0 +1,60 @@
++alias org.eolang.txt.concat
++alias org.eolang.txt.split
++alias org.eolang.txt.at
++alias org.eolang.txt.substring
++alias org.eolang.txt.length
++alias org.eolang.seq
++alias org.eolang.array
++architect [email protected]
++home https://github.com/objectionary/eo
++package org.eolang.io
++version 0.0.0
++unlint unit-test-missing
++spdx SPDX-FileCopyrightText: Copyright (c) 2016-2026 Objectionary.com
++spdx SPDX-License-Identifier: MIT
+
+# The `sprintf` object formats a string using a template and arguments.
+#
+# Example:
+# ```
+# sprintf > message
+#   "Hello %s!"
+#   (array "World")
+# ```
+[format args] > sprintf
+  # Simple implementation handling %s and %%
+  format.split "%" > parts
+  parts.at 0 > result
+
+  seq > @
+    parts.slice 1 parts.length > remaining
+    remaining.each-with-index > part i
+      if.
+        part.length.gt 0
+        seq
+          part.substring 0 1 > first
+          if.
+            first.eq "%"
+            # Escaped %%
+            seq
+              result.write (concat result "%")
+              part.substring 1 part.length > rest
+              if.
+                rest.length.gt 0
+                result.write (concat result rest)
+            if.
+              first.eq "s"
+              seq
+                # String substitution
+                args.at i > arg
+                result.write (concat result (string arg))
+                part.substring 1 part.length > rest
+                if.
+                  rest.length.gt 0
+                  result.write (concat result rest)
+              # Unknown specifier, keep as is
+              seq
+                result.write (concat result "%")
+                result.write (concat result part)
+        result
+    result