Switch to an expression-based language design

The previous approach required both assignment and call statements to be
matched last which is impossible. An expression-based language design
simplifies the parser and provides useful syntax to programmers (such as
a ternary operator in the form of assigning the result of an if
statement). This commit does not provide an implementation.

1 files changed, 5 insertions, 6 deletions

diff --git a/doc/grammar.txt b/doc/grammar.txt
index d92f1dc..4df88d7 100644
--- a/doc/grammar.txt
+++ b/doc/grammar.txt
@@ -16,7 +16,7 @@ constant := [ COMMENT ]
 
 block := "{" command* "}"
 
-command := block | statement | control
+command := block | statement
 
 control := if | for
 
@@ -24,8 +24,6 @@ statement := ( return
 		| break
 		| continue
 		| declaration
-		| assignment
-		| call
 		| defer ) ";"
 
 if := "if" expression block elseif* else*
@@ -42,11 +40,11 @@ continue := "continue" ":" NAME
 declaration := "let" [ "mut" ] NAME "=" expression ";"
 
 assignment := location "=" expression ";"
-location := NAME ( index | field )* [ "*" ]
+location := path ( index | field )* [ "*" ]
 index := "[" expression "]"
 field := "." NAME
 
-call := path "(" ( expression ), ")"
+call := location "(" ( expression ), ")"
 
 defer := "defer" call
 
@@ -81,7 +79,8 @@ bitsummand := bitfactor ( "^" | bitfactor )*
 bitfactor := unaryprefix ( "&" unaryprefix )*
 unaryprefix := [ "-" | "!" | "~" ] unarypostfix
 unarypostfix := primary [ "*" | "?" | "!" ]
-primary := grouping | literal | call | path
+primary := control | grouping | literal | named
+named := assignment | call | location
 grouping := "(" expression ")"
 literal := bool | string | number | arrayelems
 bool := "true" | "false"