parse-error

Author: keiravillekode

exercises/practice/wordy/.meta/example.el

@@ -4,22 +4,26 @@
 
 ;;; Code:
 
+(define-error 'parse-error "unable to understand question")
+
 (defun calculate (left tokens)
   (if (null tokens)
     left
     (let ((operation (car tokens)))
       (cond
+        ((null (cdr tokens)) (signal 'parse-error nil))
         ((string= operation "plus") (calculate (+ left (string-to-number (cadr tokens))) (drop 2 tokens)))
         ((string= operation "minus") (calculate (- left (string-to-number (cadr tokens))) (drop 2 tokens)))
-        ((and (string= operation "multiplied") (string= (cadr tokens) "by")) (calculate (* left (string-to-number (caddr tokens))) (drop 3 tokens)))
-        ((and (string= operation "divided") (string= (cadr tokens) "by")) (calculate (/ left (string-to-number (caddr tokens))) (drop 3 tokens)))
-        (t (error "unknown operation"))))))
+        ((string= operation "multiplied-by") (calculate (* left (string-to-number (cadr tokens))) (drop 2 tokens)))
+        ((string= operation "divided-by") (calculate (/ left (string-to-number (cadr tokens))) (drop 2 tokens)))
+        (t (signal 'parse-error nil))))))
 
 (defun answer (question)
-  (unless (string= (substring question -1) "?") (error "syntax error"))
-  (let ((tokens (split-string (substring question 0 -1))))
-    (unless (string= (car tokens) "What") (error "unknown operation"))
-    (unless (string= (cadr tokens) "is") (error "unknown operation"))
+  (unless (string= (substring question -1) "?") (signal 'parse-error nil))
+  (let ((tokens (split-string (string-replace " by" "-by" (substring question 0 -1)))))
+    (unless (string= (car tokens) "What") (signal 'parse-error nil))
+    (unless (string= (cadr tokens) "is") (signal 'parse-error nil))
+    (unless (cddr tokens) (signal 'parse-error nil))
     (calculate (string-to-number (caddr tokens)) (drop 3 tokens))))
 
 

exercises/practice/wordy/.meta/tests.toml

@@ -12,9 +12,21 @@
 [88bf4b28-0de3-4883-93c7-db1b14aa806e]
 description = "just a number"
 
+[18983214-1dfc-4ebd-ac77-c110dde699ce]
+description = "just a zero"
+
+[607c08ee-2241-4288-916d-dae5455c87e6]
+description = "just a negative number"
+
 [bb8c655c-cf42-4dfc-90e0-152fcfd8d4e0]
 description = "addition"
 
+[bb9f2082-171c-46ad-ad4e-c3f72087c1b5]
+description = "addition with a left hand zero"
+
+[6fa05f17-405a-4742-80ae-5d1a8edb0d5d]
+description = "addition with a right hand zero"
+
 [79e49e06-c5ae-40aa-a352-7a3a01f70015]
 description = "more addition"
 

exercises/practice/wordy/wordy-test.el

@@ -13,10 +13,26 @@
   (should (= 5 (answer "What is 5?"))))
 
 
+(ert-deftest just-a-zero ()
+  (should (= 0 (answer "What is 0?"))))
+
+
+(ert-deftest just-a-negative-number ()
+  (should (= -123 (answer "What is -123?"))))
+
+
 (ert-deftest addition ()
   (should (= 2 (answer "What is 1 plus 1?"))))
 
 
+(ert-deftest addition-with-a-left-hand-zero ()
+  (should (= 2 (answer "What is 0 plus 2?"))))
+
+
+(ert-deftest addition-with-a-right-hand-zero ()
+  (should (= 3 (answer "What is 3 plus 0?"))))
+
+
 (ert-deftest more-addition ()
   (should (= 55 (answer "What is 53 plus 2?"))))
 
@@ -70,35 +86,35 @@
 
 
 (ert-deftest unknown-operation ()
-  (should-error (answer "What is 52 cubed?")))
+  (should-error (answer "What is 52 cubed?") :type 'parse-error))
 
 
 (ert-deftest non-math-question ()
-  (should-error (answer "Who is the President of the United States?")))
+  (should-error (answer "Who is the President of the United States?") :type 'parse-error))
 
 
 (ert-deftest reject-problem-missing-an-operand ()
-  (should-error (answer "What is 1 plus?")))
+  (should-error (answer "What is 1 plus?") :type 'parse-error))
 
 
 (ert-deftest reject-problem-with-no-operands-or-operators ()
-  (should-error (answer "What is?")))
+  (should-error (answer "What is?") :type 'parse-error))
 
 
 (ert-deftest reject-two-operations-in-a-row ()
-  (should-error (answer "What is 1 plus plus 2?")))
+  (should-error (answer "What is 1 plus plus 2?") :type 'parse-error))
 
 
 (ert-deftest reject-two-numbers-in-a-row ()
-  (should-error (answer "What is 1 plus 2 1?")))
+  (should-error (answer "What is 1 plus 2 1?") :type 'parse-error))
 
 
 (ert-deftest reject-postfix-notation ()
-  (should-error (answer "What is 1 2 plus?")))
+  (should-error (answer "What is 1 2 plus?") :type 'parse-error))
 
 
 (ert-deftest reject-prefix-notation ()
-  (should-error (answer "What is plus 1 2?")))
+  (should-error (answer "What is plus 1 2?") :type 'parse-error))
 
 
 (provide 'wordy-test)

exercises/practice/wordy/wordy.el

@@ -5,6 +5,10 @@
 ;;; Code:
 
 
+(define-error 'parse-error
+              (error "Delete this S-Expression and write your own implementation"))
+
+
 (defun answer (question)
   (error "Delete this S-Expression and write your own implementation"))