Prolog: update denotational_semantics problems

1 files changed, 32 insertions, 0 deletions

diff --git a/prolog/problems/algol/algol_3/en.py b/prolog/problems/algol/algol_3/en.py
new file mode 100644
index 0000000..3b91a47
--- /dev/null
+++ b/prolog/problems/algol/algol_3/en.py
@@ -0,0 +1,32 @@
+name = 'algol/3'
+slug = 'interpreter for mini-algol'
+
+description = '''\
+<p>A DCG for mini-algol.</p>
+<pre>
+% apply a function to a starting state
+?- apply([a=2], Out, fun(_In, Out, eval(a+3, _In, Out))).
+  Out = 5.
+
+% a := a+b
+% b := a-b
+% a := a-b
+?- _Program = [begin,a,:=,a+b,b,:=,a-b,a,:=,a-b,end],
+    algol(_F, _Program, []),
+    apply([a=3,b=5], Output, _F).
+  Output = [a=5,b=3,printout=[]].
+
+% a := 0
+% while a < 10 do
+% begin
+%   print(a)
+%   a := a+1
+% end
+?- _Program = [begin,a,:=,0,while,a,<,10,do,begin,print(a),a,:=,a+1,end,end],
+    algol(_F, _Program, []),
+    apply([a=3], Output, _F).
+  Output = [a=10,printout=[0,1,2,3,4,5,6,7,8,9]].
+</pre>
+'''
+
+hint = {}