add error handling & numpy to readme

diff --git a/README.md b/README.md
index 5911843..8daf28c 100644 (file)
--- a/README.md
+++ b/README.md
@@ -3,4 +3,4 @@ matrixnullspace.com
 
 A [WSGI](http://www.python.org/dev/peps/pep-0333/) application to calculate the the kernel, determinant and eigenvalues of a given matrix.
 
-Requires [SciPy](http://www.scipy.org/).
+Requires [SciPy](http://www.scipy.org/) and [NumPy](https://en.wikipedia.org/wiki/NumPy).

diff --git a/matrix.py b/matrix.py
index 41713e2..f7da2d7 100755 (executable)
--- a/matrix.py
+++ b/matrix.py
@@ -13,13 +13,25 @@ def calculate_eigenvalues(A, eps=1e-15):
     u, s, vh = svd(A)
     return s
 
+def fail(start_response, message):
+    start_response('400 Bad Request', [])
+    return 'error: ' + message
+
 def application(environ, start_response):
-    parameters = cgi.parse_qs(environ.get('QUERY_STRING', ''))
+    parameters = cgi.parse_qs(environ.get('QUERY_STRING'))
 
+    if not 'matrix' in parameters or parameters['matrix'] == '':
+        return fail(start_response, 'missing matrix')
     query_string = str(parameters['matrix'][0])
     matrix = query_string.splitlines()
     for index, row in enumerate(matrix):
         matrix[index] = row.split()
+        if len(matrix[index]) != len(matrix[0]):
+            return fail(start_response, 'ragged matrix')
+        for index, n in enumerate(matrix[index]):
+            try: float(n)
+            except ValueError:
+                return fail(start_response, 'invalid matrix element')
 
     while len(matrix) < len(matrix[0]):
         matrix.append([0]*len(matrix[0]))