Add main.c for a driver demo

main.c

@@ -0,0 +1,72 @@
+/*
+ * Simple REPL for the calc evaluator.
+ * Build: calc main.c -o calc -lm
+ * @author Abner Coimbre <abner@terminal.click>
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <assert.h>
+#include <ctype.h>
+
+/* Macros expected by tc_calc.h / tc_calc.c */
+#define function static
+#define global   static
+#define cast(T)  (T)
+
+#ifndef TC_CALC_FORMAT_BUFFER_SIZE
+#define TC_CALC_FORMAT_BUFFER_SIZE 256
+#endif
+
+#include "tc_calc.h"
+#include "tc_calc.c"
+
+#define INPUT_MAX 1024
+
+int main(void)
+{
+    char buf[INPUT_MAX];
+    calc_FormatKind fmt = CALC_FORMAT_DECIMAL;
+
+    printf("calc> ");
+    fflush(stdout);
+
+    while (fgets(buf, sizeof buf, stdin)) {
+        /* strip trailing newline */
+        buf[strcspn(buf, "\n")] = '\0';
+
+        /* skip blank lines */
+        if (buf[0] == '\0') {
+            printf("calc> ");
+            fflush(stdout);
+            continue;
+        }
+
+        /* format switching commands */
+        if (strcmp(buf, ":dec") == 0) {
+            fmt = CALC_FORMAT_DECIMAL;
+            printf("  format: decimal\n");
+        } else if (strcmp(buf, ":hex") == 0) {
+            fmt = CALC_FORMAT_HEX;
+            printf("  format: hex\n");
+        } else if (strcmp(buf, ":bin") == 0) {
+            fmt = CALC_FORMAT_BINARY;
+            printf("  format: binary\n");
+        } else {
+            double result = calc_eval(buf);
+
+            if (isnan(result))
+                printf("  error: invalid expression\n");
+            else
+                printf("  %s\n", calc_format_result(result, fmt));
+        }
+
+        printf("calc> ");
+        fflush(stdout);
+    }
+
+    putchar('\n');
+    return 0;
+}