feat(library): add experimental string LEFT function

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/pseudocode-lib/README.md b/pseudocode-lib/README.md
index 92a4bbb..b776d16 100644
--- a/pseudocode-lib/README.md
+++ b/pseudocode-lib/README.md
@@ -17,4 +17,6 @@ INCLUDE paths are relative to the program. Adjust them when the program is elsew
 
 `_EXP_STRING` owns an unbounded `std::string` through one handle. Constructors accept no arguments, another `_EXP_STRING`, `C_STRING`, or `(INTEGER count, C_CHAR character)`. Cast literals to C types explicitly; built-in STRING is not a constructor argument. Copy construction and assignment own independent strings. `_HANDLE` is public only for library implementation access; do not modify or free it.
 
-The first version provides `&`, `_EXP_STRING_NUM_TO_STR` (INTEGER/REAL), `_EXP_STRING_STR_TO_NUM` (REAL), `_EXP_STRING_LENGTH` (byte length) and `_EXP_STRING_OUTPUT` (text plus newline). Numeric formatting uses `std::to_string`; parsing uses `std::stod` and requires full consumption. C++ standard exceptions print the user call line and are catchable with TRY/CATCH. The built-in STRING remains available with its existing lifetime and NUL limitations. Owning class values inside whole-record or BYVAL-array copies still have bitwise-copy limitations.
+The library provides `&`, `_EXP_STRING_NUM_TO_STR` (INTEGER/REAL), `_EXP_STRING_STR_TO_NUM` (REAL), `_EXP_STRING_LENGTH` (byte length) and `_EXP_STRING_OUTPUT` (text plus newline). Numeric formatting uses `std::to_string`; parsing uses `std::stod` and requires full consumption. C++ standard exceptions print the user call line and are catchable with TRY/CATCH. The built-in STRING remains available with its existing lifetime and NUL limitations. Owning class values inside whole-record or BYVAL-array copies still have bitwise-copy limitations.
+
+`_EXP_STRING_LEFT(S : _EXP_STRING, Count : INTEGER)` returns a new `_EXP_STRING` containing up to Count bytes from the beginning. Nonpositive counts return an empty string; counts exceeding the length return the whole string. Embedded NUL bytes are preserved.