diff --git a/app.cpp b/app.cpp
index 1808c0f..915e93e 100644
--- a/app.cpp
+++ b/app.cpp
@@ -143,19 +143,19 @@ int gymTrackerStatus(Arena *arena, list<string> args) {
         GymLogDbParsed *db = parseDb(arena, os_readEntireFile(arena, DB_FILE_LOCATION));
 
         Timestamp startTs = {0};
-        int numDays = 1;
+        ParsePositiveIntResult numDays = {1, false};
         bool showAll = args.length == 1 && strEql(args.data[0], "--all"_s);
         if (!showAll) {
             if (args.length == 2 && (strEql(args.data[0], "--days"_s) || strEql(args.data[0], "-d"_s))) {
                 size_t l;
                 numDays = parsePositiveInt(args.data[1], &l);
             }
-            if (numDays == -1) {
+            if (!numDays.valid) {
                 puts("Bad argument for --days (-d) parameter.");
                 statusCode = 1;
             } else {
                 uint64 todayUnix = getSystemUnixTime();
-                UnixTimestamp startUnix = todayUnix - numDays * 24 * 60 * 60;
+                UnixTimestamp startUnix = todayUnix - numDays.result * 24 * 60 * 60;
                 startTs = timestampFromUnixTime(&startUnix);
             }
         }
@@ -267,14 +267,14 @@ int gymTrackerDeleteEntries(Arena *arena, list<string> args) {
         statusCode = 1;
     } else {
         size_t position = 0;
-        int numToDelete = parsePositiveInt(args.data[0], &position);
-        if (numToDelete != -1) {
+        ParsePositiveIntResult numToDeleteParsed = parsePositiveInt(args.data[0], &position);
+        if (numToDeleteParsed.valid) {
             list<GymLogEntry> logEntries = loadEntryLog(arena, LOG_FILE_LOCATION);
-            if (numToDelete > logEntries.length) {
-                log("%i is more than the current number of log entries (%i). Aborting.", numToDelete, logEntries.length);
+            if (numToDeleteParsed.result > logEntries.length) {
+                log("%i is more than the current number of log entries (%i). Aborting.", numToDeleteParsed, logEntries.length);
                 statusCode = 1;
             } else {
-                os_writeEntireFile(arena, LOG_FILE_LOCATION, (byte *)logEntries.data, (logEntries.length - numToDelete) * sizeof(GymLogEntry));
+                os_writeEntireFile(arena, LOG_FILE_LOCATION, (byte *)logEntries.data, (logEntries.length - numToDeleteParsed.result) * sizeof(GymLogEntry));
             }
         } else {
             log("Invalid number to delete.\n");
@@ -321,17 +321,18 @@ int gymTrackerDo(Arena *arena, list<string> args) {
     if (statusCode == 0) {
         exercise.id = existingEntry->id;
         size_t parsedCount = 0;
-        real32 kg = parsePositiveReal32(args.data[1], &parsedCount);
-        uint8 reps = parsePositiveInt(args.data[2], &parsedCount);
-        if (parsedCount == 0 || kg == NAN || reps == 0 || kg == 0) {
+        ParsePositiveReal32Result kg = parsePositiveReal32(args.data[1], &parsedCount);
+        ParsePositiveIntResult reps = parsePositiveInt(args.data[2], &parsedCount);
+        if (!kg.valid || !reps.valid) {
+            log("%zu, %f, %\n", parsedCount, kg, reps);
             log("Invalid reps or weight input.\n");
             statusCode = 1;
         } else {
             GymLogEntry entry = {
                 getSystemUnixTime(),
                 exercise.id,
-                reps,
-                kg,
+                reps.result,
+                kg.result,
             };
 
             os_fileAppend(arena, LOG_FILE_LOCATION, (byte *)&entry, sizeof(entry));
diff --git a/djstdlib/core.cpp b/djstdlib/core.cpp
index c08b51b..0f931ca 100644
--- a/djstdlib/core.cpp
+++ b/djstdlib/core.cpp
@@ -274,7 +274,7 @@ list<string> strSplit(Arena *arena, string splitStr, string inputStr) {
     return result;
 }
 
-int8 parsePositiveInt(string str, size_t *lengthPointer) {
+ParsePositiveIntResult parsePositiveInt(string str, size_t *lengthPointer) {
     size_t numEnd = 0;
     char currChar = str.str[numEnd];
     while (numEnd < str.length && isNumeric(currChar)) {
@@ -288,14 +288,14 @@ int8 parsePositiveInt(string str, size_t *lengthPointer) {
             result *= 10;
             result += str.str[i] - '0';
         }
-        return result;
+        return {result, true};
     } else {
-        return -1;
+        return {0, false};
     }
 }
 
-real32 parsePositiveReal32(string str, size_t *lengthPointer) {
-    real32 result = NAN;
+ParsePositiveReal32Result parsePositiveReal32(string str, size_t *lengthPointer) {
+    ParsePositiveReal32Result result = {NAN, false};
 
     string wholePartStr = string{0};
     string fractionalPartStr = string{0};
@@ -314,16 +314,21 @@ real32 parsePositiveReal32(string str, size_t *lengthPointer) {
         c++;
     }
     if (split) {
-        int wholePart = parsePositiveInt(wholePartStr, lengthPointer);
+        ParsePositiveIntResult wholePartParsed = parsePositiveInt(wholePartStr, lengthPointer);
         *lengthPointer += 1;
-        int fractionalPart = parsePositiveInt(fractionalPartStr, lengthPointer);
-        if (wholePart >= 0 && fractionalPart >= 0) {
+        ParsePositiveIntResult fractionalPartParsed = parsePositiveInt(fractionalPartStr, lengthPointer);
+        if (wholePartParsed.valid && fractionalPartParsed.valid) {
             // TODO(dledda): implement powf with intrinsics? or just custom
             real32 fractionalPartMultiplier = 1.0f / powf(10.0f, (real32)fractionalPartStr.length);
-            result = (real32)wholePart + (real32)fractionalPart * (real32)fractionalPartMultiplier;
+            result.result = (real32)wholePartParsed.result + (real32)fractionalPartParsed.result * (real32)fractionalPartMultiplier;
+            result.valid = true;
         }
     } else if (c > 0) {
-        result = (real32)parsePositiveInt(str, lengthPointer);
+        ParsePositiveIntResult intPartParsed = parsePositiveInt(str, lengthPointer);
+        if (intPartParsed.valid) {
+            result.result = (real32)intPartParsed.result;
+            result.valid = true;
+        }
     }
     return result;
 }
diff --git a/djstdlib/core.h b/djstdlib/core.h
index 2889d13..7a82d5a 100644
--- a/djstdlib/core.h
+++ b/djstdlib/core.h
@@ -176,8 +176,10 @@ list<string> strSplit(Arena *arena, string splitStr, string inputStr);
 string strPrintfv(Arena *arena, const char *fmt, va_list args);
 string strPrintf(Arena *arena, const char *fmt, ...);
 
-int8 parsePositiveInt(string str, size_t *lengthPointer); 
-real32 parsePositiveReal32(Arena *arena, string str, size_t *lengthPointer); 
+struct ParsePositiveIntResult { uint8 result; bool valid; };
+ParsePositiveIntResult parsePositiveInt(string str, size_t *lengthPointer); 
+struct ParsePositiveReal32Result { real32 result; bool valid; };
+ParsePositiveReal32Result parsePositiveReal32(Arena *arena, string str, size_t *lengthPointer); 
 
 inline function bool isNumeric(char c);