# HG changeset patch
# User Kai T. Ohlhus <k.ohlhus@gmail.com>
# Date 1635734168 -32400
# Node ID 38ee67b5ec9f95f8a710b76879ed837d87915eb9
# Parent  3c60814448ea063ab891c8d89267264448bd3f49
input.cc: throw error if second argument does not equal 's'

Same behavior with Matlab R2021a and is indeed confusing for users coming from
the C-programming language.  See for example Octave Discourse

https://octave.discourse.group/t/calling-the-input-function-with-two-arguments/1749

diff -r 3c60814448ea -r 38ee67b5ec9f libinterp/corefcn/input.cc
--- a/libinterp/corefcn/input.cc	Sun Oct 31 18:25:33 2021 +0100
+++ b/libinterp/corefcn/input.cc	Mon Nov 01 11:36:08 2021 +0900
@@ -695,12 +695,18 @@
   {
     octave_value_list retval;
 
-    int read_as_string = 0;
+    std::string prompt = args(0).xstring_value ("input: unrecognized argument");
 
-    if (args.length () == 2)
-      read_as_string++;
+    bool read_as_string = false;
+    if (args.length () == 2)  // `input (..., "s")`?
+      {
+        std::string literal
+          = args(1).xstring_value ("input: second argument must be 's'.");
+        if (literal.length () != 1 || literal[0] != 's')
+          error ("input: second argument must be 's'.");
 
-    std::string prompt = args(0).xstring_value ("input: unrecognized argument");
+        read_as_string = true;
+      }
 
     output_system& output_sys = m_interpreter.get_output_system ();