From 4b6c8abc75f18b5ff7c75fbebab0f39c7a485009 Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Mon, 28 Sep 2020 14:29:17 +0200
Subject: [PATCH] jitters: eval: add evaluator function

---
 src/eval/evaluator.c | 46 ++++++++++++++++++++++++++++++++++++++++++++
 src/eval/evaluator.h |  8 ++++++++
 src/eval/local.am    |  4 ++++
 src/local.am         |  1 +
 4 files changed, 59 insertions(+)
 create mode 100644 src/eval/evaluator.c
 create mode 100644 src/eval/evaluator.h
 create mode 100644 src/eval/local.am

diff --git a/src/eval/evaluator.c b/src/eval/evaluator.c
new file mode 100644
index 0000000..fd7e140
--- /dev/null
+++ b/src/eval/evaluator.c
@@ -0,0 +1,46 @@
+#include "evaluator.h"
+
+static int evaluate_unop(const struct unop_node *un_op)
+{
+    switch (un_op->op)
+    {
+    case IDENTITY:
+        return evaluate_ast(un_op->rhs);
+    case NEGATE:
+        return -evaluate_ast(un_op->rhs);
+    default:
+        return 0;
+    }
+}
+
+static int evaluate_binop(const struct binop_node *bin_op)
+{
+    switch (bin_op->op)
+    {
+    case PLUS:
+        return evaluate_ast(bin_op->lhs) + evaluate_ast(bin_op->rhs);
+    case MINUS:
+        return evaluate_ast(bin_op->lhs) - evaluate_ast(bin_op->rhs);
+    case TIMES:
+        return evaluate_ast(bin_op->lhs) * evaluate_ast(bin_op->rhs);
+    case DIVIDE:
+        return evaluate_ast(bin_op->lhs) / evaluate_ast(bin_op->rhs);
+    default:
+        return 0;
+    }
+}
+
+int evaluate_ast(const struct ast_node *ast)
+{
+    switch (ast->kind)
+    {
+    case NUM:
+        return ast->val.num;
+    case UNOP:
+        return evaluate_unop(&ast->val.un_op);
+    case BINOP:
+        return evaluate_binop(&ast->val.bin_op);
+    default:
+        return 0;
+    }
+}
diff --git a/src/eval/evaluator.h b/src/eval/evaluator.h
new file mode 100644
index 0000000..70c982e
--- /dev/null
+++ b/src/eval/evaluator.h
@@ -0,0 +1,8 @@
+#ifndef EVALUATOR_H
+#define EVALUATOR_H
+
+#include "ast/ast.h"
+
+int evaluate_ast(const struct ast_node *ast);
+
+#endif /* !EVALUATOR_H */
diff --git a/src/eval/local.am b/src/eval/local.am
new file mode 100644
index 0000000..f0f187b
--- /dev/null
+++ b/src/eval/local.am
@@ -0,0 +1,4 @@
+jitters_SOURCES += \
+    %D%/evaluator.c \
+    %D%/evaluator.h \
+    $(NULL)
diff --git a/src/local.am b/src/local.am
index a548005..79f1590 100644
--- a/src/local.am
+++ b/src/local.am
@@ -15,5 +15,6 @@ AM_CPPFLAGS = -I$(top_builddir)/src -I$(top_srcdir)/src
 jitters_LDADD =
 
 include %D%/ast/local.am
+include %D%/eval/local.am
 include %D%/parse/local.am
 include %D%/print/local.am