support string equality in the interpreter

src/eval/interpreter.zig

@@ -97,6 +97,7 @@ pub const EvalError = error{
     StringInterpolationFailed,
     StringSegmentEvaluationFailed,
     StringConversionFailed,
+    StringOrderingNotSupported,
     UnsupportedWorkItem,
     UnexpectedWorkItem,
     RuntimeCrash,
@@ -1526,8 +1527,32 @@ pub const Interpreter = struct {
                         self.traceError("comparison operations on fractional types only support Dec precision", .{});
                         return error.TypeMismatch;
                     }
+                }
+                // Check if both operands are strings
+                else if (lhs_scalar.tag == .str and rhs_scalar.tag == .str) {
+                    const lhs_ptr = @as(*const RocStr, @ptrCast(@alignCast(lhs.ptr.?)));
+                    const rhs_ptr = @as(*const RocStr, @ptrCast(@alignCast(rhs.ptr.?)));
+                    const lhs_str = lhs_ptr.*;
+                    const rhs_str = rhs_ptr.*;
+
+                    const result_layout = Layout.boolType();
+                    var result_value = try self.pushStackValue(result_layout);
+
+                    const bool_result: u8 = switch (kind) {
+                        .w_binop_eq => if (lhs_str.eq(rhs_str)) 1 else 0,
+                        .w_binop_ne => if (!lhs_str.eq(rhs_str)) 1 else 0,
+                        // String ordering comparisons are not implemented yet
+                        .w_binop_gt, .w_binop_lt, .w_binop_ge, .w_binop_le => {
+                            self.traceError("string ordering comparisons (>, <, >=, <=) are not supported", .{});
+                            return error.StringOrderingNotSupported;
+                        },
+                        else => unreachable,
+                    };
+
+                    result_value.setBool(bool_result);
+                    self.traceInfo("String comparison: \"{s}\" {s} \"{s}\" = {}", .{ lhs_str.asSlice(), @tagName(kind), rhs_str.asSlice(), bool_result });
                 } else {
-                    self.traceError("comparison operations require operands of the same type (both integers or both decimals)", .{});
+                    self.traceError("comparison operations require operands of the same type (both integers, both decimals, or both strings)", .{});
                     return error.TypeMismatch;
                 }
             },

test/snapshots/repl/string_edge_cases.md

@@ -0,0 +1,43 @@
+# META
+~~~ini
+description=String comparison edge cases and longer strings
+type=repl
+~~~
+# SOURCE
+~~~roc
+» longStr1 = "This is a very long string that should test the comparison of larger strings that might not fit in small string optimization"
+» longStr2 = "This is a very long string that should test the comparison of larger strings that might not fit in small string optimization"
+» longStr3 = "This is a very long string that should test the comparison of larger strings that might not fit in small string optimizatioN"
+» longStr1 == longStr2
+» longStr1 == longStr3
+» whitespace1 = "hello "
+» whitespace2 = "hello"
+» whitespace1 == whitespace2
+» specialChars1 = "hello\nworld"
+» specialChars2 = "hello\nworld"
+» specialChars1 == specialChars2
+~~~
+# OUTPUT
+assigned `longStr1`
+---
+assigned `longStr2`
+---
+assigned `longStr3`
+---
+True
+---
+False
+---
+assigned `whitespace1`
+---
+assigned `whitespace2`
+---
+False
+---
+assigned `specialChars1`
+---
+assigned `specialChars2`
+---
+True
+# PROBLEMS
+NIL

test/snapshots/repl/string_equality_basic.md

@@ -0,0 +1,31 @@
+# META
+~~~ini
+description=Basic string equality comparisons
+type=repl
+~~~
+# SOURCE
+~~~roc
+» "hello" == "hello"
+» "hello" == "world"
+» "hello" != "world"
+» "hello" != "hello"
+» "" == ""
+» "" == "not empty"
+» "same length" == "different.."
+~~~
+# OUTPUT
+True
+---
+False
+---
+True
+---
+False
+---
+True
+---
+False
+---
+False
+# PROBLEMS
+NIL

test/snapshots/repl/string_interpolation_comparison.md

@@ -0,0 +1,31 @@
+# META
+~~~ini
+description=String interpolation and concatenation comparisons
+type=repl
+~~~
+# SOURCE
+~~~roc
+» name = "World"
+» "Hello, ${name}!" == "Hello, World!"
+» "Hello, ${name}!" == "Hello, Earth!"
+» prefix = "Got: "
+» suffix = "test"
+» "${prefix}${suffix}" == "Got: test"
+» "${prefix}${suffix}" != "Got: different"
+~~~
+# OUTPUT
+assigned `name`
+---
+True
+---
+False
+---
+assigned `prefix`
+---
+assigned `suffix`
+---
+True
+---
+True
+# PROBLEMS
+NIL

test/snapshots/repl/string_multiline_comparison.md

@@ -0,0 +1,18 @@
+# META
+~~~ini
+description=Simple multiline string comparison
+type=repl
+~~~
+# SOURCE
+~~~roc
+» foo =
+"""first line
+"""second line
+» foo == "first line\nsecond line"
+~~~
+# OUTPUT
+assigned `foo`
+---
+True
+# PROBLEMS
+NIL

test/snapshots/repl/string_ordering_unsupported.md

@@ -0,0 +1,22 @@
+# META
+~~~ini
+description=String ordering operations should fail gracefully (not supported)
+type=repl
+~~~
+# SOURCE
+~~~roc
+» "apple" > "banana"
+» "zoo" < "aardvark"
+» "equal" >= "equal"
+» "first" <= "second"
+~~~
+# OUTPUT
+Evaluation error: error.StringOrderingNotSupported
+---
+Evaluation error: error.StringOrderingNotSupported
+---
+Evaluation error: error.StringOrderingNotSupported
+---
+Evaluation error: error.StringOrderingNotSupported
+# PROBLEMS
+NIL