*

3 files changed, 28 insertions, 4 deletions

diff --git a/lua/chupacabra/chupacabra.lua b/lua/chupacabra/chupacabra.lua
index e64afc3..562dc6b 100644
--- a/lua/chupacabra/chupacabra.lua
+++ b/lua/chupacabra/chupacabra.lua
@@ -60,6 +60,22 @@ function chupacabra.evaluate(tokens, context)
             local b = table.remove(stack)
             table.insert(stack, a)
             table.insert(stack, b)
+        elseif token == "=" then
+            local b = table.remove(stack)
+            local a = table.remove(stack)
+            table.insert(stack, a == b)
+        elseif token == "@=" then
+            -- checks if the values of 2 equally lenghted arrays are equal, and returns a bit mask of the differences
+            local b = table.remove(stack)
+            local a = table.remove(stack)
+            if #a ~= #b then
+                error("Arrays must have equal length")
+            end
+            local result = {}
+            for i = 1, #a do
+                table.insert(result, a[i] == b[i])
+            end
+            table.insert(stack, result)
         elseif token == "@" then
             local index = table.remove(stack)
             local array = table.remove(stack)
diff --git a/lua/chupacabra/refcard.md b/lua/chupacabra/refcard.md
index a2b473c..26aa4f5 100644
--- a/lua/chupacabra/refcard.md
+++ b/lua/chupacabra/refcard.md
@@ -9,15 +9,17 @@ Chupacabra is a stack-based programming language/calculator implemented in lua.
 - **Numbers**: You can push numbers onto the stack. For example, `1` pushes the number 1 onto the stack.
 - **Arrays**: You can push arrays onto the stack. For example, `[1 2 3 4]` pushes the array {1, 2, 3, 4} onto the stack.
 - **`.`**: The `.` operator pops the top element from the stack and discards it.
-- **`:`**: The `:` operator duplicates the top element of the stack
-- **`?`**: The `?` operator swaps the top two elements of the stack
+- **`:`**: The `:` operator duplicates the top element of the stack.
+- **`?`**: The `?` operator swaps the top two elements of the stack.
+- **`=`**: The `=` operators checks the top two elements of the stack are equal. Arrays can never be equal, only their values can be.
 
 ## Array-first keywords
-- **`@`**: the `@` keyword allows you to grab a specific value from an array by index, e.g. `[10 20 30] 2 @` would return the value `20`.
+- **`@`**: The `@` keyword allows you to grab a specific value from an array by index, e.g. `[10 20 30] 2 @` would return the value `20`.
 - **`@+`**: The `@+` keyword adds the top two elements on the stack. It supports addition between two numbers, a number and an array, or two arrays.
 - **`@-`**: The `@-` keyword subtracts the second topmost element on the stack from the topmost element. It supports subtraction between two numbers, a number and an array, or two arrays.
 - **`@*`**: The `@*` keyword multiplies the top two elements on the stack. It supports multiplication between two numbers, a number and an array, or two arrays.
 - **`@/`**: The `@/` keyword divides the topmost element on the stack by the second topmost element. It supports division between two numbers, a number and an array, or two arrays.
+- **`@=`**: The `@=` keyword compares two equal length arrays and returns an array (like a bit-mask). 
 
 ## Test cases
 You can create test cases using the `tc` function from lua. The `tc` function takes an input string and an expected output, runs the input string through the Chupacabra interpreter, and checks if the output matches the expected output.
diff --git a/lua/chupacabra/test_chupacabra.lua b/lua/chupacabra/test_chupacabra.lua
index 0a58cc4..e2f54b1 100644
--- a/lua/chupacabra/test_chupacabra.lua
+++ b/lua/chupacabra/test_chupacabra.lua
@@ -48,4 +48,10 @@ tc("[1 2 3 4 5] [6 7 8 9 10] [10 11 12 13] @..", {1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
 tc("[10 20 30] 1 @", 10)  -- access array element at a given index (1-based)
 tc("[10 20 30] 2 @ 20 +", 40)  -- this leaves nothing on the stack, since @ consumes the array and doesn't replace it on to the stack
 tc("1 2 3 : +", 6) -- : duplicates the top element on the stack
-tc("100 10 20 ?", 10) -- ? swaps the top two elements on the stack
\ No newline at end of file
+tc("100 10 20 ?", 10) -- ? swaps the top two elements on the stack
+tc("1 1 =", true) -- = compares the top two elements on the stack
+tc("1 2 =", false)
+tc("[1 2 3] [1 2 3] =", false) -- arrays are not equal, but their values can be
+tc("[1 2 3] [1 2 3] @=", {true, true, true})
+tc("[1 2 3] [1 2 4] @=", {true, true, false})
+