Addition with floats is now entirely possible.

Makefile

@@ -14,7 +14,7 @@ TEST_OBJ_DIR = $(TEST_BUILD_DIR)/obj
 CC = clang
 LINK = clang
 CFLAGS = -Wall -DDBG -ggdb
-LDFLAGS =
+LDFLAGS = -lm
 
 SRC_FILES = $(wildcard $(SRC_DIR)/*.c)
 OBJ_FILES = $(patsubst $(SRC_DIR)/%.c, $(OBJ_DIR)/%.o, $(SRC_FILES))

src/grammar.y

@@ -35,13 +35,13 @@ input:
     ;
 
 exp:
-    NUM { $$ = ast_init(AST_TYPE_NUM, ast_type_num_init($1)); }
+    NUM { $$ = ast_init(AST_TYPE_NUM, ast_num_data_init($1)); }
     | NUM PLUS NUM {
         AST* argv[2] = {
-            ast_init(AST_TYPE_NUM, ast_type_num_init($1)),
-            ast_init(AST_TYPE_NUM, ast_type_num_init($3))
+            ast_init(AST_TYPE_NUM, ast_num_data_init($1)),
+            ast_init(AST_TYPE_NUM, ast_num_data_init($3))
         };
-        $$ = ast_init(AST_TYPE_CALL, ast_type_call_init("+", 2, argv));
+        $$ = ast_init(AST_TYPE_CALL, ast_call_data_init("+", 2, argv));
     };
 
 %%

src/include/lexer.h

@@ -17,6 +17,12 @@
 extern YYSTYPE yylval;
 extern char* inp;
 
+// Accumulate an integer.
+int acc_int(int c);
+
+// Accumulate a floating-point number.
+double acc_float(int c);
+
 // Called by `yyparse()` (in bison-generated files.)
 int yylex();
 void yyerror(char const* s);

src/lexer.c

@@ -1,9 +1,45 @@
 #include <ctype.h>
 #include <limits.h>
 #include <stdio.h>
+#include <math.h>
 
 #include "include/lexer.h"
 
+int acc_int(int c) {
+    int value = c - '0';
+    while (isdigit(*inp)) {
+        value = value * 10 + (*inp - '0'); // Accumulate value.
+        inp++;
+    }
+    return value;
+}
+
+double acc_float(int c) {
+    double value = (double)(c - '0');
+
+    // Grab everything prior to '.'.
+    while (isdigit(*inp)) {
+        value = value * 10 + (*inp - '0'); // Accumulate value.
+        inp++;
+    }
+
+    if (*inp ==  '.') {
+        char* oinp = inp++;
+        while (isdigit(*inp)) {
+            // Accumulate as int, divide once at end.
+            value = value + (((double)(*inp - '0'))/pow(10.0l, (double)(inp-oinp))); // Accumulate value.
+            inp++;
+        }
+    }
+
+    // > 1.20000
+    // = 1.0 + 2/10
+
+    // > 1.23
+    // = 1.2 + 3/100
+    return value;
+}
+
 int yylex() {
     if (*inp == '\0') return YYEOF;
 
@@ -15,12 +51,7 @@ int yylex() {
 
     // Check for NUM.
     if (isdigit(c)) {
-        int value = c - '0';
-        while (isdigit(*inp)) {
-            value = value * 10 + (*inp - '0'); // Accumulate value.
-            inp++;
-        }
-        yylval.fval = value; // Set the token value.
+        yylval.fval = acc_float(c); // Set the token value.
         return NUM;
     }