fp-interop: Apply suggestions from PR review

Author: kc9jud

proposals/fp_interop/25-xxx.txt

@@ -4,17 +4,25 @@ Subject: Requirements and specifications for interoperability with C
          interchange and extended types
 Date: 2025-Oct-XX
 
-Reference:
+References:
+      ISO/IEC 9899:2024 Programming languages -- C ("C23")
+            (working draft N3220)
+      WG5/N2249 Fortran 202Y Work Items
+      23-176 Add extended floating-point types defined in ISO C23
+            to ISO_C_BINDING
+      ISO/IEC 60559:2020 Floating-Point arithmetic
+      IEEE 754-2019 IEEE Standard for Floating-Point Arithmetic
+
 
 1 Background
 ============
 
 bg01. The ISO C23 specification (ISO/IEC 9899:2024) added support for
-      interchange and extended floating-point types. The current Fortran
-      202Y work list WG5/N2249 includes adding interoperability with
-      these types as accepted work item US05. At meeting #230 in June
-      2023, J3 accepted paper 23-176 as background/use-case for
-      additional interchange types.
+      interchange and extended floating-point types (C23 Annex H). The
+      current Fortran 202Y work list WG5/N2249 includes adding
+      interoperability with these types as accepted work item US05. At
+      meeting #230 in June 2023, J3 accepted paper 23-176 as
+      background/use-case for additional interchange types.
 
 bg03. This paper contains formal requirements and specifications for
       Fortran 202Y proposal US05, "Add extended floating-point types
@@ -23,7 +31,18 @@ bg03. This paper contains formal requirements and specifications for
 2 Requirements
 ==============
 
-rq01. The ISO_C_BINDING module should provide integer named constants
+rq01. The C23 standard adds a large number of new types, importing
+      significant portions of ISO/IEC 60559 (a.k.a IEEE 754) into its
+      specification. The most important of these for Fortran
+      interoperability with C are the '_Float16', '_Float32',
+      '_Float64', and '_Float128' types (and their related complex
+      types). Requirements rq02-r05 deal with these new types. Many of
+      the other types, covered by rq07-rq17, are marked as optional and
+      could be dropped independently while keeping the rest of this
+      paper. These optional requirements primarily serve to maintain
+      parity with Annex H of C23.
+
+rq02. The ISO_C_BINDING module should provide integer named constants
       for KIND parameters corresponding to the C interchange floating
       types '_Float16', '_Float32', '_Float64', and '_Float128'.
 
@@ -94,7 +113,7 @@ sp02. To the ISO_C_BINDING module, add the following integer named
       If the companion processor defines '__STDC_IEC_60559_BFP__' and
       '__STDC_IEC_60559_TYPES__', then the constants 'C_FLOAT32' and
       'C_FLOAT64' should have the same values as 'C_FLOAT' and
-      'C_DOUBLE' (C2023 H.2.4.2).
+      'C_DOUBLE', respectively (C2023 H.2.4.2).
 
 sp05. To the ISO_C_BINDING module, add the following integer named
       constants for real KIND parameters: