feat(frontends/lean): use #"c" instead of 'c' for character literals

The new notation is the same one used in Standard ML.
It will also allow us to use ' in the beginning of identifiers like Standard ML.

library/debugger/util.lean

@@ -5,7 +5,7 @@ Authors: Leonardo de Moura
 -/
 namespace debugger
 def is_space (c : char) : bool :=
-if c = ' ' ∨ c = char.of_nat 11 ∨ c = '\n' then tt else ff
+if c = #" " ∨ c = char.of_nat 11 ∨ c = #"\n" then tt else ff
 
 def split_core : string → string → list string
 | (c::cs) [] :=
@@ -22,7 +22,7 @@ def to_qualified_name_core : string → string → name
 | []      r := if r = [] then name.anonymous else mk_simple_name r^.reverse
 | (c::cs) r :=
   if is_space c then to_qualified_name_core cs r
-  else if c = '.' then
+  else if c = #"." then
        if r = [] then to_qualified_name_core cs []
        else           name.mk_string r^.reverse (to_qualified_name_core cs [])
   else to_qualified_name_core cs (c::r)

library/init/char.lean

@@ -28,4 +28,4 @@ have decidable_eq (fin char_sz), from fin.decidable_eq _,
 this
 
 instance : inhabited char :=
-⟨'A'⟩
+⟨#"A"⟩

library/init/string.lean

@@ -41,7 +41,7 @@ def utf8_length : string → nat
 private def to_nat_core : list char → nat → nat
 | []      r := r
 | (c::cs) r :=
-  to_nat_core cs (char.to_nat c - char.to_nat '0' + r*10)
+  to_nat_core cs (char.to_nat c - char.to_nat #"0" + r*10)
 
 def string.to_nat (s : string) : nat :=
 to_nat_core s^.reverse 0

library/init/to_string.lean

@@ -51,14 +51,13 @@ instance {A : Type u} {P : A → Prop} [has_to_string A] : has_to_string (subtyp
 ⟨λ s, to_string (elt_of s)⟩
 
 def char.quote_core (c : char) : string :=
-if       c = '\n' then "\\n"
-else if  c = '\\' then "\\\\"
-else if  c = '\"' then "\\\""
-else if  c = '\'' then "\\\'"
+if       c = #"\n" then "\\n"
+else if  c = #"\\" then "\\\\"
+else if  c = #"\"" then "\\\""
 else c::nil
 
 instance : has_to_string char :=
-⟨λ c, "'" ++ char.quote_core c ++ "'"⟩
+⟨λ c, "#\"" ++ char.quote_core c ++ "\""⟩
 
 def string.quote_aux : string → string
 | []      := ""

src/frontends/lean/scanner.cpp

@@ -178,12 +178,14 @@ auto scanner::read_string() -> token_kind {
 }
 
 auto scanner::read_char() -> token_kind {
+    lean_assert(curr() == '\"');
+    next();
     char c = curr();
     if (c == '\\')
         c = read_quoted_char(g_end_error_char_msg);
     next();
-    if (curr() != '\'')
-        throw_exception("invalid character, ' expected");
+    if (curr() != '"')
+        throw_exception("invalid character, \" expected");
     next();
     m_buffer.clear();
     m_buffer += c;
@@ -535,18 +537,18 @@ auto scanner::read_key_cmd_id() -> token_kind {
 
 static name * g_begin_comment_tk        = nullptr;
 static name * g_begin_comment_block_tk  = nullptr;
-static name * g_tick_tk                 = nullptr;
+static name * g_pound_tk                = nullptr;
 
 void initialize_scanner() {
     g_begin_comment_tk       = new name("--");
     g_begin_comment_block_tk = new name("/-");
-    g_tick_tk                = new name("'");
+    g_pound_tk               = new name("#");
 }
 
 void finalize_scanner() {
     delete g_begin_comment_tk;
     delete g_begin_comment_block_tk;
-    delete g_tick_tk;
+    delete g_pound_tk;
 }
 
 auto scanner::scan(environment const & env) -> token_kind {
@@ -581,7 +583,7 @@ auto scanner::scan(environment const & env) -> token_kind {
                         read_single_line_comment();
                     else if (n == *g_begin_comment_block_tk)
                         read_comment_block();
-                    else if (n == *g_tick_tk)
+                    else if (n == *g_pound_tk && curr() == '"')
                         return read_char();
                     else
                         return k;

src/frontends/lean/token_table.cpp

@@ -88,7 +88,7 @@ void init_token_table(token_table & t) {
          {"(:", g_max_prec}, {":)", 0},
          {"⊢", 0}, {"⟨", g_max_prec}, {"⟩", 0}, {"^", 0}, {"↑", 0}, {"▸", 0},
          {"//", 0}, {"|", 0}, {"!", g_max_prec}, {"?", 0},  {"with", 0}, {"without", 0}, {"...", 0}, {",", 0},
-         {".", 0}, {":", 0}, {"::", 0}, {"calc", 0}, {"as", 0}, {":=", 0}, {"--", 0}, {"#", 0},
+         {".", 0}, {":", 0}, {"::", 0}, {"calc", 0}, {"as", 0}, {":=", 0}, {"--", 0}, {"#", g_max_prec},
          {"(*", 0}, {"/-", 0}, {"begin", g_max_prec}, {"using", 0},
          {"@@", g_max_prec}, {"@", g_max_prec},
          {"sorry", g_max_prec}, {"+", g_plus_prec}, {"->", g_arrow_prec}, {"<-", 0},

src/library/string.cpp

@@ -47,9 +47,9 @@ static void display_char_literal_core(std::ostream & out, char c, bool in_string
 }
 
 static void display_char_literal(std::ostream & out, char c) {
-    out << "'";
+    out << "#\"";
     display_char_literal_core(out, c, false);
-    out << "'";
+    out << "\"";
 }
 
 static void display_string_literal(std::ostream & out, std::string const & s) {

tests/lean/char_lits.lean

@@ -1,11 +1,11 @@
 import system.io
 
-check 'a'
+check #"a"
 
-vm_eval 'a'
-vm_eval '\n'
-vm_eval '\\'
-vm_eval put_str (list.cons '\\' "aaa")
-vm_eval put_str ['\n']
-vm_eval put_str ['\n']
-vm_eval put_str (list.cons '\'' "aaa")
+vm_eval #"a"
+vm_eval #"\n"
+vm_eval #"\\"
+vm_eval put_str (list.cons #"\\" "aaa")
+vm_eval put_str [#"\n"]
+vm_eval put_str [#"\n"]
+vm_eval put_str (list.cons #"\'" "aaa")

tests/lean/char_lits.lean.expected.out

@@ -1,7 +1,7 @@
-'a' : char
-'a'
-'\n'
-'\\'
+#"a" : char
+#"a"
+#"\n"
+#"\\"
 aaa\
 
 

tests/lean/curly_notation.lean

@@ -5,7 +5,7 @@ check ({} : set nat)
 definition s1 : set nat := {1, 2+3, 3, 4}
 print s1
 
-definition s2 : set char := {'a', 'b', 'c'}
+definition s2 : set char := {#"a", #"b", #"c"}
 print s2
 
 definition s3 : set string := {"hello", "world"}

tests/lean/curly_notation.lean.expected.out

@@ -4,7 +4,7 @@
 definition s1 : set ℕ :=
 {1, 2 + 3, 3, 4}
 definition s2 : set char :=
-{'a', 'b', 'c'}
+{#"a", #"b", #"c"}
 definition s3 : set string :=
 {"hello", "world"}
 {a ∈ s1 | a > 1} : set ℕ

tests/lean/hex_char.lean

@@ -1,3 +1,3 @@
-vm_eval '\x41'
-vm_eval '\x42'
-vm_eval '\x43'
+vm_eval #"\x41"
+vm_eval #"\x42"
+vm_eval #"\x43"

tests/lean/hex_char.lean.expected.out

@@ -1,3 +1,3 @@
-'A'
-'B'
-'C'
+#"A"
+#"B"
+#"C"