From b20c46c555986a99be70de61d91bc225e53f31d2 Mon Sep 17 00:00:00 2001
From: hachem <im@hachem.wtf>
Date: Sat, 19 Sep 2026 11:52:25 +0200
Subject: eval: sum product and quotient

---
 ast.h                |  3 +++
 eval.c               | 46 +++++++++++++++++++++++++++++++++++++++++++---
 eval.h               |  4 +++-
 examples/sums.sfinae |  3 +++
 sfinae.l             |  3 +++
 sfinae.y             |  9 +++++++++
 6 files changed, 64 insertions(+), 4 deletions(-)
 create mode 100644 examples/sums.sfinae

diff --git a/ast.h b/ast.h
index 1a6f159..778a765 100644
--- a/ast.h
+++ b/ast.h
@@ -5,6 +5,9 @@ enum NodeKind
     NODE_CHAR,
     TYPE_DECLTYPE,
     VALUE_DIFFERENCE,
+    VALUE_SUM,
+    VALUE_PRODUCT,
+    VALUE_QUOTIENT,
     STMT_EMIT
 };
 
diff --git a/eval.c b/eval.c
index 5841566..f9f47b6 100644
--- a/eval.c
+++ b/eval.c
@@ -1,14 +1,54 @@
 #include <assert.h>
+#include <inttypes.h>
 #include <stdio.h>
 
 #include "eval.h"
 
-static int evaluate_value(const struct Node* node, long* out)
+static int evaluate_value(const struct Node* node, int64_t* out);
+
+static int complain(const struct Node* node, const char* message)
+{
+    (void)fprintf(stderr, "line %d: %s\n", node->line, message);
+    return 1;
+}
+
+static int evaluate_operands(const struct Node* node, int64_t* left, int64_t* right)
 {
+    if (evaluate_value(node->first, left))
+        return 1;
+
+    return evaluate_value(node->second, right);
+}
+
+static int evaluate_value(const struct Node* node, int64_t* out)
+{
+    int64_t left = 0;
+    int64_t right = 0;
     switch (node->kind)
     {
         case VALUE_DIFFERENCE:
-            *out = (long)node->first->character - (long)node->second->character;
+            *out = (int64_t)node->first->character - (int64_t)node->second->character;
+            return 0;
+        case VALUE_SUM:
+            if (evaluate_operands(node, &left, &right))
+                return 1;
+
+            *out = left + right;
+            return 0;
+        case VALUE_PRODUCT:
+            if (evaluate_operands(node, &left, &right))
+                return 1;
+
+            *out = left * right;
+            return 0;
+        case VALUE_QUOTIENT:
+            if (evaluate_operands(node, &left, &right))
+                return 1;
+
+            if (right == 0)
+                return complain(node, "division by zero");
+
+            *out = left / right;
             return 0;
         default: break;
     }
@@ -42,7 +82,7 @@ static enum RunStatus emit(const struct Node* node)
         return RUN_FAILED;
 
     if (type.kind == KIND_VALUE)
-        (void)printf("%ld\n", type.number);
+        (void)printf("%" PRId64 "\n", type.number);
     return RUN_DONE;
 }
 
diff --git a/eval.h b/eval.h
index 8b4a5f6..49101f1 100644
--- a/eval.h
+++ b/eval.h
@@ -2,6 +2,8 @@
 
 #include "ast.h"
 
+#include <stdint.h>
+
 enum TypeKind
 {
     KIND_VOID,
@@ -11,7 +13,7 @@ enum TypeKind
 struct Type
 {
     enum TypeKind kind;
-    long number;
+    int64_t number;
 };
 
 enum RunStatus
diff --git a/examples/sums.sfinae b/examples/sums.sfinae
new file mode 100644
index 0000000..b5ffb62
--- /dev/null
+++ b/examples/sums.sfinae
@@ -0,0 +1,3 @@
+::emit<::decltype(::sum<::difference<'F', 'A'>, ::difference<'C', 'A'>>)>::commit;
+::emit<::decltype(::product<::difference<'D', 'A'>, ::difference<'E', 'A'>>)>::commit;
+::emit<::decltype(::quotient<::difference<'H', 'A'>, ::difference<'C', 'A'>>)>::commit;
diff --git a/sfinae.l b/sfinae.l
index 5c67f3c..5857a2b 100644
--- a/sfinae.l
+++ b/sfinae.l
@@ -36,6 +36,9 @@ static int fail(const char* message)
 "commit"                return TOK_COMMIT;
 "decltype"              return TOK_DECLTYPE;
 "difference"            return TOK_DIFFERENCE;
+"sum"                   return TOK_SUM;
+"product"               return TOK_PRODUCT;
+"quotient"              return TOK_QUOTIENT;
 [<>(),;]                return yytext[0];
 '\\.'                   yylval.character = unescape(yytext[2]); return TOK_CHAR;
 '.'                     yylval.character = yytext[1]; return TOK_CHAR;
diff --git a/sfinae.y b/sfinae.y
index 2e91b23..3e7c9b1 100644
--- a/sfinae.y
+++ b/sfinae.y
@@ -20,6 +20,9 @@ void yyerror(const char* message);
 %token TOK_COMMIT
 %token TOK_DECLTYPE
 %token TOK_DIFFERENCE
+%token TOK_SUM
+%token TOK_PRODUCT
+%token TOK_QUOTIENT
 %token <character> TOK_CHAR
 
 %type <node> statements statement type value
@@ -51,6 +54,12 @@ type
 value
     : TOK_COLONCOLON TOK_DIFFERENCE '<' TOK_CHAR ',' TOK_CHAR '>'
         { $$ = node_binary(VALUE_DIFFERENCE, node_char($4), node_char($6)); }
+    | TOK_COLONCOLON TOK_SUM '<' value ',' value '>'
+        { $$ = node_binary(VALUE_SUM, $4, $6); }
+    | TOK_COLONCOLON TOK_PRODUCT '<' value ',' value '>'
+        { $$ = node_binary(VALUE_PRODUCT, $4, $6); }
+    | TOK_COLONCOLON TOK_QUOTIENT '<' value ',' value '>'
+        { $$ = node_binary(VALUE_QUOTIENT, $4, $6); }
     ;
 
 %%
-- 
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