Added findStringInstance function to strings package

packages/strings/readme.md

@@ -2,26 +2,30 @@
 
 This library adds extra string manipulation functions to ground. It is entirely coded in ground.
 
-Please note that you cannot copy a single function from the package, as some functions rely on other functions in the library.
+Please note that you cannot copy a single function from the package, as some functions rely on other functions in the library (reliance on other functions is detailed below). 
 
 ## Functions
 
 ### fun -char !findChar -string &str -char &char
 
-Finds the index of $char in $string
+Finds the index of $char in $string (no prerequisites).
 
 ### fun -char !findCharInstance -string &str -char &char -int &instance
 
-Finds the index of the `$instance`th instance of $char in $str
+Finds the index of the `$instance`th instance of $char in $str (no prerequisites).
 
 ### fun -string !mid -string &str -int &idx -int &len
 
-Finds $len characters of $str, starting at $idx.
+Finds $len characters of $str, starting at $idx (no prerequisites).
 
 ### fun -string !inBrackets -string &str -char &left -char &right -int &instance
 
-Finds the content of the `$instance`th instance of brackets, with the left bracket being the $left char and the right bracket of $right char.
+Finds the content of the `$instance`th instance of brackets, with the left bracket being the $left char and the right bracket of $right char (requires !findCharInstance).
 
 ### fun -string !matchStart -string &str -string &instr
 
-Checks if the start of $str matches $instr.
+Checks if the start of $str matches $instr (requires !mid).
+
+### fun -int !findStringInstance -string &str -string &instr -int &instance
+
+The same as !findCharInstance, but allows a string to be parsed to be searched for (no prerequisites).

packages/strings/strings.grnd

@@ -82,4 +82,41 @@ fun -string !matchStart -string &str -string &instr
     call !mid &store
     equal $store $instr &store
     return $store
+endfun
+
+fun -int !findStringInstance -string &str -string &instr -int &instance
+    getstrsize $instr &len
+    subtract $len 1 &len
+    set &idx $len
+
+    @loop
+        set &tempstr ""
+        subtract $idx $len &tempidx
+        subtract $tempidx 1 &tempidx
+        @subloop
+            equal $tempidx $idx &store
+            if $store %continue
+            add $tempidx 1 &tempidx
+
+            getstrcharat $str $tempidx &store
+            add $tempstr $store &tempstr
+            jump %subloop
+
+
+        @continue
+        equal $tempstr $instr &store
+        if $store %decrement
+        add $idx 1 &idx
+        jump %loop
+    
+        @decrement
+        equal $instance 0 &store
+        if $store %end
+        subtract $instance 1 &instance
+        add $idx 1 &idx
+        jump %loop
+
+    @end
+    subtract $idx $len &idx
+    return $idx
 endfun