make \cdot, \interpunct, and \cdotp equivalent (JuliaLang#25157)

Co-authored-by: Steven G. Johnson <stevenj@alum.mit.edu>

Co-authored-by: Steven G. Johnson <stevenj@alum.mit.edu>

NEWS.md

@@ -14,7 +14,9 @@ New language features
 
 Language changes
 ----------------
+
 * `macroexpand`, `@macroexpand`, and `@macroexpand1` no longer wrap errors in a `LoadError`. To reduce breakage, `@test_throws` has been modified so that many affected tests will still pass ([#38379]].
+* The middle dot `·` (`\cdotp` U+00b7) and the Greek interpunct `·` (U+0387) are now treated as equivalent to the dot operator `⋅` (`\cdot` U+22c5) (#25157).
 
 Compiler/Runtime improvements
 -----------------------------

doc/src/manual/variables.md

@@ -136,9 +136,13 @@ ERROR: syntax: unexpected "="
 Some Unicode characters are considered to be equivalent in identifiers.
 Different ways of entering Unicode combining characters (e.g., accents)
 are treated as equivalent (specifically, Julia identifiers are [NFC](http://www.macchiato.com/unicode/nfc-faq)-normalized).
-The Unicode characters `ɛ` (U+025B: Latin small letter open e)
-and `µ` (U+00B5: micro sign) are treated as equivalent to the corresponding
-Greek letters, because the former are easily accessible via some input methods.
+Julia also includes a few non-standard equivalences for characters that are
+visually similar and are easily entered by some input methods. The Unicode
+characters `ɛ` (U+025B: Latin small letter open e) and `µ` (U+00B5: micro sign)
+are treated as equivalent to the corresponding Greek letters. The middle dot
+`·` (U+00B7) and the Greek
+[interpunct](https://en.wikipedia.org/wiki/Interpunct) `·` (U+0387) are both
+treated as the mathematical dot operator `⋅` (U+22C5).
 
 ## Stylistic Conventions
 

src/flisp/julia_charmap.h

@@ -4,4 +4,6 @@
 static const uint32_t charmap[][2] = {
     { 0x025B, 0x03B5 }, // latin small letter open e -> greek small letter epsilon
     { 0x00B5, 0x03BC }, // micro sign -> greek small letter mu
+    { 0x00B7, 0x22C5 }, // middot char -> dot operator (#25098)
+    { 0x0387, 0x22C5 }, // Greek interpunct -> dot operator (#25098)
 };

src/flisp/julia_extensions.c

@@ -351,6 +351,15 @@ value_t fl_accum_julia_symbol(fl_context_t *fl_ctx, value_t *args, uint32_t narg
     return symbol(fl_ctx, allascii ? str.buf : normalize(fl_ctx, str.buf));
 }
 
+/* convert a string to a symbol, first applying normalization */
+value_t fl_string2normsymbol(fl_context_t *fl_ctx, value_t *args, uint32_t nargs)
+{
+    argcount(fl_ctx, "string->normsymbol", nargs, 1);
+    if (!fl_isstring(fl_ctx, args[0]))
+        type_error(fl_ctx, "string->normsymbol", "string", args[0]);
+    return symbol(fl_ctx, normalize(fl_ctx, (char*)cvalue_data(args[0])));
+}
+
 static const builtinspec_t julia_flisp_func_info[] = {
     { "skip-ws", fl_skipws },
     { "accum-julia-symbol", fl_accum_julia_symbol },
@@ -360,6 +369,7 @@ static const builtinspec_t julia_flisp_func_info[] = {
     { "op-suffix-char?", fl_julia_op_suffix_char },
     { "strip-op-suffix", fl_julia_strip_op_suffix },
     { "underscore-symbol?", fl_julia_underscore_symbolp },
+    { "string->normsymbol", fl_string2normsymbol },
     { NULL, NULL }
 };
 

src/julia-parser.scm

@@ -21,7 +21,7 @@
 (define prec-colon       (append! '(: |..|) (add-dots '(… ⁝ ⋮ ⋱ ⋰ ⋯))))
 (define prec-plus        (append! '($)
                           (add-dots '(+ - ¦ |\|| ⊕ ⊖ ⊞ ⊟ |++| ∪ ∨ ⊔ ± ∓ ∔ ∸ ≏ ⊎ ⊻ ⊽ ⋎ ⋓ ⧺ ⧻ ⨈ ⨢ ⨣ ⨤ ⨥ ⨦ ⨧ ⨨ ⨩ ⨪ ⨫ ⨬ ⨭ ⨮ ⨹ ⨺ ⩁ ⩂ ⩅ ⩊ ⩌ ⩏ ⩐ ⩒ ⩔ ⩖ ⩗ ⩛ ⩝ ⩡ ⩢ ⩣))))
-(define prec-times       (add-dots '(* / ⌿ ÷ % & ⋅ ∘ × |\\| ∩ ∧ ⊗ ⊘ ⊙ ⊚ ⊛ ⊠ ⊡ ⊓ ∗ ∙ ∤ ⅋ ≀ ⊼ ⋄ ⋆ ⋇ ⋉ ⋊ ⋋ ⋌ ⋏ ⋒ ⟑ ⦸ ⦼ ⦾ ⦿ ⧶ ⧷ ⨇ ⨰ ⨱ ⨲ ⨳ ⨴ ⨵ ⨶ ⨷ ⨸ ⨻ ⨼ ⨽ ⩀ ⩃ ⩄ ⩋ ⩍ ⩎ ⩑ ⩓ ⩕ ⩘ ⩚ ⩜ ⩞ ⩟ ⩠ ⫛ ⊍ ▷ ⨝ ⟕ ⟖ ⟗ ⨟)))
+(define prec-times       (add-dots '(* / ⌿ ÷ % & · · ⋅ ∘ × |\\| ∩ ∧ ⊗ ⊘ ⊙ ⊚ ⊛ ⊠ ⊡ ⊓ ∗ ∙ ∤ ⅋ ≀ ⊼ ⋄ ⋆ ⋇ ⋉ ⋊ ⋋ ⋌ ⋏ ⋒ ⟑ ⦸ ⦼ ⦾ ⦿ ⧶ ⧷ ⨇ ⨰ ⨱ ⨲ ⨳ ⨴ ⨵ ⨶ ⨷ ⨸ ⨻ ⨼ ⨽ ⩀ ⩃ ⩄ ⩋ ⩍ ⩎ ⩑ ⩓ ⩕ ⩘ ⩚ ⩜ ⩞ ⩟ ⩠ ⫛ ⊍ ▷ ⨝ ⟕ ⟖ ⟗ ⨟)))
 (define prec-rational    (add-dots '(//)))
 (define prec-bitshift    (add-dots '(<< >> >>>)))
 ;; `where`
@@ -234,7 +234,7 @@
   (if (and (eqv? c0 #\*) (eqv? (peek-char port) #\*))
       (error "use \"x^y\" instead of \"x**y\" for exponentiation, and \"x...\" instead of \"**x\" for splatting."))
   (if (or (eof-object? (peek-char port)) (not (op-or-sufchar? (peek-char port))))
-      (symbol (string c0)) ; 1-char operator
+      (string->normsymbol (string c0)) ; 1-char operator
       (let ((str (let loop ((str (string c0))
                             (c   (peek-char port))
                             (in-suffix? #f))
@@ -267,7 +267,7 @@
                                           (loop newop (peek-char port) sufchar?))
                                    str))
                              str))))))
-        (string->symbol str))))
+        (string->normsymbol str))))
 
 (define (accum-digits c pred port _-digit-sep)
   (let loop ((str '())

test/syntax.jl

@@ -819,7 +819,7 @@ let f = function (x; kw...)
 end
 
 # normalization of Unicode symbols (#19464)
-let ε=1, μ=2, x=3, î=4
+let ε=1, μ=2, x=3, î=4, ⋅=5
     # issue #5434 (mu vs micro):
     @test Meta.parse("\u00b5") === Meta.parse("\u03bc")
     @test µ == μ == 2
@@ -829,6 +829,9 @@ let ε=1, μ=2, x=3, î=4
     # latin vs greek ε (#14751)
     @test Meta.parse("\u025B") === Meta.parse("\u03B5")
     @test ɛ == ε == 1
+    # middot char · or · vs math dot operator ⋅ (#25098)
+    @test Meta.parse("\u00b7") === Meta.parse("\u0387") === Meta.parse("\u22c5")
+    @test (·) == (·) == (⋅) == 5
 end
 
 # issue #8925