diff options
Diffstat (limited to 'spec')
| -rw-r--r-- | spec/grammar.md | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/spec/grammar.md b/spec/grammar.md index 90f4718b..df355c77 100644 --- a/spec/grammar.md +++ b/spec/grammar.md @@ -47,12 +47,18 @@ Functions can be formed by applying modifiers, or with trains. Modifiers are lef FuncExpr = Train | F ASGN FuncExpr -Subject expressions are complicated by the possibility of list and namespace assignment, which share the nodes `lhsList` and `lhsStr` and cannot be completely distinguished until execution. We also define nothing-statements, which have very similar syntax to subject expressions but do not permit assignment. +Subject expressions consist mainly of function application. We also define nothing-statements, which have very similar syntax to subject expressions but do not permit assignment. They can be used as an `STMT` or in place of a left argument. arg = subExpr | ( subject | nothing )? Derv arg nothing = "·" | ( subject | nothing )? Derv nothing + subExpr = arg + | lhs ASGN subExpr + | lhs Derv "↩" subExpr? # Modified assignment + +The target of subject assignment can be compound to allow for destructuring. List and namespace assignment share the nodes `lhsList` and `lhsStr` and cannot be completely distinguished until execution. The term `sl` in `LHS_SUB` is used for header inputs below: as an additional rule, it cannot be used in the `lhs` term of a `subExpr` node. + NAME = s | F | _m | _c_ LHS_SUB = "·" | lhsList | sl LHS_ANY = NAME | LHS_SUB | "(" LHS_ELT ")" @@ -63,9 +69,6 @@ Subject expressions are complicated by the possibility of list and namespace ass lhsList = "⟨" ⋄? ( ( LHS_ENTRY ⋄ )* LHS_ENTRY ⋄? )? "⟩" lhsComp = LHS_SUB | lhsStr | "(" lhs ")" lhs = s | lhsComp - subExpr = arg - | lhs ASGN subExpr - | lhs Derv "↩" subExpr? # Modified assignment A header looks like a name for the thing being headed, or its application to inputs (possibly twice in the case of modifiers). As with assignment, it is restricted to a simple form with no extra parentheses. The full list syntax is allowed for arguments. A plain name is called a label and can be used for a block with or without arguments. First we define headers `IMM_HEAD` that include no arguments. |