initial commit

1 files changed, 43 insertions, 0 deletions

diff --git a/parser.py b/parser.py
new file mode 100644
index 0000000..6360b62
--- /dev/null
+++ b/parser.py
@@ -0,0 +1,43 @@
+from tokens import *
+
+
+def peek(inp):
+    if len(inp) == 0:
+        return None
+    return inp[0]
+
+def parse_expression(tkns):
+    # expressions MUST start with a symbol (for now?)
+    symbol = None
+    args = []
+    for idx, t in enumerate(tkns):
+        #if isinstance(t, NebOpen):
+        if idx == 0:
+            if not isinstance(t, NebSymbol):
+                raise Exception("expressions must start with a symbol")
+            else:
+                symbol = t
+        elif isinstance(t, NebClose):
+            return NebExpression(symbol, args), tkns[idx + 1:]
+        else:  # TODO nested expressions
+            args.append(t)
+            
+    raise Exception("couldn't parse expression!")
+
+def parse(tkns, parsed):
+    nxt = peek(tkns)
+    if nxt is None:
+        return parsed
+    if isinstance(nxt, NebOpen):
+        expr, remainder = parse_expression(tkns[1:])
+        parsed.append(expr)
+        return parse(remainder, parsed)
+    elif isinstance(nxt, NebLiteral):
+        parsed.append(nxt)
+        return parse(tkns[1:], parsed)
+    elif isinstance(nxt, NebSymbol):
+        parsed.append(nxt)
+        return parse(tkns[1:], parsed)
+    else:
+        raise Exception("expecting an expression or a literal")
+