feat(exercises): Add tricks track exercise

Author: tekkac

.patches/tricks/no_conditionals.cairo.patch

@@ -0,0 +1,12 @@
+--- a/exercises/tricks/no_conditionals.cairo	2022-06-02 14:49:04.224066616 +0200
++++ a/exercises/tricks/no_conditionals.cairo	2022-06-02 14:46:49.463087238 +0200
+@@ -28,2 +28,2 @@
+-    # FILL ME
+-    return (res)
++    let (not_zero) = is_not_zero((x - 1) * x)
++    return (res=1 - not_zero)
+@@ -37 +37,3 @@
+-    # FILL ME
++    let tmp = (x - 1337) * (x - 69420) * (x - 42)
++    let (s) = is_not_zero(tmp)
++    let res = s * 'meh' + (1 - s) * 'cool'

exercises/tricks/no_conditionals.cairo

@@ -0,0 +1,68 @@
+%lang starknet
+
+from starkware.cairo.common.math_cmp import is_not_zero
+
+# Sometimes, conditionals can be avoided by using an expression that
+# - maps valid inputs to 1,
+# - and/or maps invalid inputs to 0.
+# For instance (row - 2) * (row - 4) is 0 only when row is 2 or 4.
+
+# Use this trick to rewrite functions without "if" conditions
+# Note: This helps to avoid dealing with revoked references.
+
+# I AM NOT DONE
+
+func is_binary_if(x : felt) -> (res : felt):
+    if x == 0:
+        return (1)
+    end
+    if x == 1:
+        return (1)
+    end
+    return (0)
+end
+
+# TODO: Return the right value to mimick the behavior of is_binary_if
+
+func is_binary_no_if(x : felt) -> (res : felt):
+    # FILL ME
+    return (res)
+end
+
+# TODO: Fix the function so that
+#  - it returns the string 'cool' if x is 1337, 69420, 42
+#  - it returns 'meh' on any other input
+
+func is_cool(x : felt) -> (res : felt):
+    # FILL ME
+    return (res)
+end
+
+# Do not change the test
+@external
+func test_is_binary{syscall_ptr : felt*}():
+    let (eval_if) = is_binary_if(0)
+    let (eval_no_if) = is_binary_no_if(0)
+    assert (eval_if, eval_no_if) = (1, 1)
+
+    let (eval_if) = is_binary_if(1)
+    let (eval_no_if) = is_binary_no_if(1)
+    assert (eval_if, eval_no_if) = (1, 1)
+
+    let (eval_if) = is_binary_if(13)
+    let (eval_no_if) = is_binary_no_if(37)
+    assert (eval_if, eval_no_if) = (0, 0)
+    return ()
+end
+
+@external
+func test_is_cool{syscall_ptr : felt*}():
+    let (is_1337_cool) = is_cool(1337)
+    let (is_69420_cool) = is_cool(69420)
+    let (is_42_cool) = is_cool(42)
+    let (is_0_cool) = is_cool(0)
+    let (is_911_cool) = is_cool(911)
+    let results = ('cool', 'cool', 'cool', 'meh', 'meh')
+    assert (is_1337_cool, is_69420_cool, is_42_cool, is_0_cool, is_911_cool) = results
+    return ()
+end

src/constants.py

@@ -20,5 +20,6 @@
     ),
     ("exercises/registers", ["registers00", "registers01", "registers02"]),
     ("exercises/revoked_references", ["revoked_references01"]),
+    ("exercises/tricks", ["no_conditionals"]),
     ("exercises/hints", ["hints00", "hints01"]),
 ]