Feat/compute powers array

src/common.cairo

@@ -9,6 +9,7 @@ mod array_extend;
 mod array_split;
 mod consts;
 mod merge_sort;
+mod powers_array;
 
 #[cfg(test)]
 mod tests;

src/common/powers_array.cairo

@@ -0,0 +1,19 @@
+// Writes the following `n` values into array:
+//   initial, initial * alpha, initial * alpha^2, ..., initial * alpha^(n - 1).
+fn powers_array(initial: felt252, alpha: felt252, n: u32) -> Array<felt252> {
+    let mut array = ArrayTrait::<felt252>::new();
+    let mut value = initial;
+    let mut i: u32 = 0;
+    loop {
+        if i == n {
+            break;
+        }
+
+        array.append(value);
+        value *= alpha;
+
+        i += 1;
+    };
+
+    array
+}

src/common/tests.cairo

@@ -5,6 +5,7 @@ mod test_horner_eval;
 mod test_array_append;
 mod test_math;
 mod test_merge_sort;
+mod test_powers_array;
 // notice: this test takes a lot of time and computation
 //         uncomment it when making changes to blake2s
 // mod test_blake2s_big;

src/common/tests/test_powers_array.cairo

@@ -0,0 +1,33 @@
+use cairo_verifier::common::powers_array::powers_array;
+
+#[test]
+#[available_gas(9999999999)]
+fn test_powers_array_0() {
+    assert(
+        powers_array(
+            8939912, 818129, 20
+        ) == array![
+            8939912,
+            7314001264648,
+            5983796540645203592,
+            4895517480001519769519368,
+            4005164820396163367517111022472,
+            3276741489345892739703406523703994888,
+            2680797237937065881240808275831425633724552,
+            2193237963476213772353661233897688422293434003208,
+            1794351581820831297361928511627481931242504867610557832,
+            1468011065283494888479417211289280164925499264833358068536328,
+            1201022424829320389616777123654887492050333788038850403253557490312,
+            982591275403187061036784251398649448983647531674436641563429735991466248,
+            578798470452897618157604965420111599212769637660707731620770014798701463210,
+            64897154080296376744067237228250081708262563085217890232603082073306308506,
+            3570855249317241879864852740142508196913411001040536104120285926502587208042,
+            296822332749766136374571546668437122679929036177024349694690002078960735182,
+            1236122849353634764512930791639952640937217569299656172828823579696019234568,
+            1554236852172389644389568626430917567621998253096118392892400158736329812430,
+            2650676934462094271980856993953144424194696459174707922062388312529884397184,
+            1618947405625354125126437534914831315303549411394098205806855140739005342069
+        ],
+        'Invalid value'
+    );
+}