2 files changed, 33 insertions, 0 deletions
diff --git a/prolog/problems/dcg/expr_2/common.py b/prolog/problems/dcg/expr_2/common.py
new file mode 100644
index 0000000..49059f2
--- /dev/null
+++ b/prolog/problems/dcg/expr_2/common.py
@@ -0,0 +1,23 @@
+id = 170
+group = 'dcg'
+number = 77
+visible = False
+facts = None
+
+solution = '''\
+expr --> term170, addterm170.
+addterm170 --> [].
+addterm170 --> [+], expr.
+term170 --> factor170, multfactor170.
+multfactor170 --> [].
+multfactor170 --> [*], term170.
+factor170 --> num170.
+factor170 --> ['('], expr, [')'].
+
+num170 --> digit170.
+num170 --> nzdigit170, num_next170.
+num_next170 --> digit170.
+num_next170 --> digit170, num_next170.
+digit170 --> ([0] ; [1] ; [2] ; [3] ; [4] ; [5] ; [6] ; [7] ; [8] ; [9]).
+nzdigit170 --> ([1] ; [2] ; [3] ; [4] ; [5] ; [6] ; [7] ; [8] ; [9]).
+'''
diff --git a/prolog/problems/dcg/expr_2/en.py b/prolog/problems/dcg/expr_2/en.py
new file mode 100644
index 0000000..9b30551
--- /dev/null
+++ b/prolog/problems/dcg/expr_2/en.py
@@ -0,0 +1,10 @@
+id = 170
+name = 'expr/2'
+slug = 'arithmetic expressions'
+
+description = '''\
+<p>Write a DCG with the starting symbol <code>expr</code> for the language of arithmetic expressions consisting of numbers (without leading zeros), addition and multiplication. Subexpressions can be grouped using parentheses.</p>
+<p>Example words: <code>(1+2)*3</code>, <code>42*8*3</code>, <code>(2+1)*(3+4)</code>.</p>
+'''
+
+hint = {}