rework log function

tact-lang · Mar 18, 2024 · 708cadc · 708cadc
1 parent 207d90c
commit 708cadc
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Showing 3 changed files with 81 additions and 8 deletions.
diff --git a/src/generator/writers/__snapshots__/writeSerialization.spec.ts.snap b/src/generator/writers/__snapshots__/writeSerialization.spec.ts.snap
@@ -2986,7 +2986,15 @@ return b.end_cell().begin_parse();",
   },
   {
     "code": {
-      "code": "return __tact_log2(num) / __tact_log2(base);",
+      "code": "if (num < base) {
+    return 0;
+}
+int result = 0;
+while (num >= base) {
+    num = num / base;
+    result += 1;
+}
+return result;",
       "kind": "generic",
     },
     "comment": null,
@@ -6833,7 +6841,15 @@ return b.end_cell().begin_parse();",
   },
   {
     "code": {
-      "code": "return __tact_log2(num) / __tact_log2(base);",
+      "code": "if (num < base) {
+    return 0;
+}
+int result = 0;
+while (num >= base) {
+    num = num / base;
+    result += 1;
+}
+return result;",
       "kind": "generic",
     },
     "comment": null,
@@ -10680,7 +10696,15 @@ return b.end_cell().begin_parse();",
   },
   {
     "code": {
-      "code": "return __tact_log2(num) / __tact_log2(base);",
+      "code": "if (num < base) {
+    return 0;
+}
+int result = 0;
+while (num >= base) {
+    num = num / base;
+    result += 1;
+}
+return result;",
       "kind": "generic",
     },
     "comment": null,

diff --git a/src/generator/writers/writeStdlib.ts b/src/generator/writers/writeStdlib.ts
@@ -1235,7 +1235,15 @@ export function writeStdlib(ctx: WriterContext) {
         ctx.context('stdlib');
         ctx.body(() => {
             ctx.write(`
-                return __tact_log2(num) / __tact_log2(base);
+                if (num < base) {
+                    return 0;
+                }
+                int result = 0;
+                while (num >= base) {
+                    num = num / base;
+                    result += 1;
+                }
+                return result;
             `);
         });
     });

diff --git a/src/test/feature-math.spec.ts b/src/test/feature-math.spec.ts
@@ -348,10 +348,51 @@ describe('feature-math', () => {
 
         for (let num = 1n; num <= 10n; num++) {
             for (let base = 2n; base <= 10; base++) {
-                const a = Math.floor(Math.log2(Number(num)));
-                const b = Math.floor(Math.log2(Number(base)));
-                const c = BigInt(Math.floor(a / b));
-                expect(await contract.getLog(num, base)).toBe(c);
+                const logarithm = BigInt(
+                    Math.floor(Math.log2(Number(num)) / Math.log2(Number(base)))
+                );
+                expect(await contract.getLog(num, base)).toBe(logarithm);
+            }
+        }
+
+        expect(await contract.getLog2(0n)).toBe(-1n);
+        expect(await contract.getLog(0n, 2n)).toBe(0n);
+
+        const maxint = 2n ** 256n - 1n;
+
+        function bigIntLogBase(num: bigint, base: bigint) {
+            let result = 0n;
+            while (num >= base) {
+                num = num / base;
+                result += 1n;
+            }
+            return result;
+        }
+
+        for (let num = maxint - 100n; num <= maxint; num++) {
+            expect(await contract.getLog2(num)).toBe(255n);
+        }
+
+        for (let num = maxint - 10n; num <= maxint; num++) {
+            for (let base = 2n; base <= 10; base++) {
+                expect(await contract.getLog(num, base)).toBe(
+                    bigIntLogBase(num, base)
+                );
+            }
+        }
+
+        for (let num = maxint / 2n - 50n; num <= maxint / 2n; num++) {
+            expect(await contract.getLog2(num)).toBe(254n);
+        }
+        for (let num = maxint / 2n + 1n; num <= maxint / 2n + 50n; num++) {
+            expect(await contract.getLog2(num)).toBe(255n);
+        }
+
+        for (let num = maxint / 2n - 5n; num <= maxint / 2n + 5n; num++) {
+            for (let base = 2n; base <= 10; base++) {
+                expect(await contract.getLog(num, base)).toBe(
+                    bigIntLogBase(num, base)
+                );
             }
         }
     });