Add p_value_get() / p_value_get_XXX() accessors

Allow user code to access specific pvalue values, especially when
multiple ptypes are in use.

assets/parser.d.erb

@@ -94,6 +94,14 @@ public <%= @grammar.prefix %>value_t <%= @grammar.prefix %>value<%= name == "def
     return <%= @grammar.prefix %>value_t(v_<%= name %>: v);
 }
 <%   end %>
+
+/** Parser value accessor(s). */
+<%   @grammar.ptypes.each do |name, typestring| %>
+public <%= typestring %> <%= @grammar.prefix %>value_get<%= name == "default" ? "" : "_#{name}" %>(<%= @grammar.prefix %>value_t * pvalue)
+{
+    return pvalue.v_<%= name %>;
+}
+<%   end %>
 <% end %>
 
 <% if @grammar.tree %>

assets/parser.h.erb

@@ -77,6 +77,14 @@ static inline <%= @grammar.prefix %>value_t <%= @grammar.prefix %>value<%= name
     return (<%= @grammar.prefix %>value_t){.v_<%= name %> = v};
 }
 <%   end %>
+
+/** Parser value accessor(s). */
+<%   @grammar.ptypes.each do |name, typestring| %>
+static inline <%= typestring %> <%= @grammar.prefix %>value_get<%= name == "default" ? "" : "_#{name}" %>(<%= @grammar.prefix %>value_t const * pvalue)
+{
+    return pvalue->v_<%= name %>;
+}
+<%   end %>
 <% end %>
 
 <% if @grammar.tree %>

doc/user_guide.md

@@ -1082,6 +1082,9 @@ The `p_token_info_t` structure contains the following fields:
 * `length` (`size_t`) holds the number of input bytes used by the token.
 * `token` (`p_token_t`) holds the token ID of the lexed token
 * `pvalue` (`p_value_t`) holds the parser value associated with the token.
+  The actual user value can be extracted with `p_value_get(&token_info.pvalue)`
+  for the default value or `p_value_get_XXX(&token_info.pvalue)` for named
+  `ptype` values.
 
 ### Tree Node Types
 
@@ -1404,18 +1407,35 @@ In this case, Propane will free a `Statement` tree structure returned by the
 
 ### `p_value`
 
-When tree generation mode is not active, the `p_value_t` union can hold one of
+The `p_value(v)` function builds an instance of the `p_value_t` with the
-several different possible value types.
-
-The `p_value(v)` function returns an instance of the `p_value_t` with the
 default member set to the value of `v`.
 
-A `p_value_XXX(v)` function is set for each user-defined `ptype` name with
+A `p_value_XXX(v)` function is defined for each user-defined `ptype` name with
 the user-given name in place of the `XXX`.
 
 These functions are useful for custom lexer functions which need to return a
 parser value corresponding to a lexed token.
 
+They are especially useful when tree generation mode is not active.
+In that case, the `p_value_t` union can hold one of several different possible
+value types.
+
+### `p_value_get`
+
+The `p_value_get()` accessor functions can be used to extract a user value
+from a `p_value_t` union.
+
+The `p_value_get(pvalue)` function accepts a pointer to a `p_value_t` and
+returns the value of its default member.
+
+A `p_value_get_XXX(pvalue)` function is generated for each user-defined `ptype`
+name with the user-given name in place of the `XXX`, returning the value of the
+corresponding member.
+
+These functions are the counterpart to `p_value()` constructor functions and
+are useful for reading the parser value associated with a lexed token, for
+example `p_value_get(&token_info.pvalue)`.
+
 ##> Data
 
 ### `p_token_names`

spec/propane_spec.rb

@@ -1781,6 +1781,39 @@ EOF
         results = run_test(language: language)
         expect(results.status).to eq 0
       end
+
+      it "provides accessor functions to extract user values from a parser value" do
+        if language == "d"
+          write_grammar <<EOF
+ptype int;
+ptype float = float;
+ptype string = string;
+
+drop /\\s+/;
+token num /\\d+/ << $$ = 42; >>
+token flt (float) /f/ << $$ = 1.5; >>
+token str (string) /s/ << $$ = "hello"; >>
+Start -> num flt str;
+EOF
+        else
+          write_grammar <<EOF
+ptype int;
+ptype float = float;
+ptype string = char *;
+
+drop /\\s+/;
+token num /\\d+/ << $$ = 42; >>
+token flt (float) /f/ << $$ = 1.5; >>
+token str (string) /s/ << $$ = (char *)"hello"; >>
+Start -> num flt str;
+EOF
+        end
+        run_propane(language: language)
+        compile("spec/test_value_accessors.#{language}", language: language)
+        results = run_test(language: language)
+        expect(results.stderr).to eq ""
+        expect(results.status).to eq 0
+      end
     end
   end
 end

spec/test_value_accessors.c

@@ -0,0 +1,29 @@
+#include "testparser.h"
+#include <assert.h>
+#include <string.h>
+
+int main()
+{
+    p_token_info_t token_info;
+    char const * input = "42 f s";
+    p_context_t * context;
+    context = p_context_new((uint8_t const *)input, strlen(input));
+
+    /* Default ptype value extracted with p_value_get(). */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_num);
+    assert(p_value_get(&token_info.pvalue) == 42);
+
+    /* Named ptype values extracted with p_value_get_XXX(). */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_flt);
+    assert(p_value_get_float(&token_info.pvalue) == 1.5);
+
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_str);
+    assert(strcmp(p_value_get_string(&token_info.pvalue), "hello") == 0);
+
+    p_context_delete(context);
+
+    return 0;
+}

spec/test_value_accessors.d

@@ -0,0 +1,29 @@
+import testparser;
+import std.stdio;
+
+int main()
+{
+    return 0;
+}
+
+unittest
+{
+    p_token_info_t token_info;
+    string input = "42 f s";
+    p_context_t * context;
+    context = p_context_new(input);
+
+    /* Default ptype value extracted with p_value_get(). */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_num);
+    assert(p_value_get(&token_info.pvalue) == 42);
+
+    /* Named ptype values extracted with p_value_get_XXX(). */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_flt);
+    assert(p_value_get_float(&token_info.pvalue) == 1.5);
+
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_str);
+    assert(p_value_get_string(&token_info.pvalue) == "hello");
+}