compound assignment

LANGUAGE.md

@@ -15,8 +15,8 @@
 - exact-width `i8` through `i64`, `u8` through `u64`, `f32`, `f64`, `isize`, `usize`, `bool`, `void`, and inferred integer-constrained `int`
 - target-dependent atomic C primitives from `c_char` through `c_longdouble`
 - C primitives remain semantically distinct from exact-width Brolang primitives until target lowering
-- contextual integer and character literals and constant folding of addition and negation trees
-- strict numeric conversions, checked integer addition, and unary negation
+- contextual integer and character literals and constant folding of arithmetic and negation trees
+- strict numeric conversions, binary `+ - * /` with checked integer overflow and divide-by-zero traps (floats follow IEEE), and unary negation
 - boolean literals, comparisons, unary `!`, and short-circuiting `and` / `or`
 - arrays `[N]T`, sentinel arrays `[N;S]T`, single-item pointers `@T`, many-item pointers `*T`, sentinel many-item pointers `[*;S]T`, pointer offsets, slices, and explicit slicing
 - immutable UTF-8 string literals typed as pointers to static sentinel arrays: `@[N;0]u8`
@@ -29,7 +29,7 @@
 - source-order native structs, defined or opaque `c_struct`, and keyed record literals
 - complete plain imported C structs and unions as runtime values; incomplete or unsupported-layout records remain pointer-only
 - C function pointer types as pointer-sized runtime values, including manual `*c_func(...) T` spelling and nullable imported callback typedefs
-- postfix pointer dereference, general writable locations, function calls, assignments, and returns
+- postfix pointer dereference, general writable locations, function calls, assignments, compound assignment (`+= -= *= /=`) with single-evaluation lvalues, and returns
 - first-class exclusive and inclusive integer ranges: `start..end` and `start..=end`
 - boolean `if` statements and `while` loops with optional post-iteration assignment/expression clauses
 - `for` loops over ranges, arrays, slices, and pointers-to-arrays, with copy, pointer, and optional `usize` index captures