X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/sod/blobdiff_plain/dea4d05507e59ab779ed4bb209e05971d87e260c..bf090e021a5c20da452a4841cdfb8eb78e29544e:/src/parser/proto-parser-expr.lisp

diff --git a/src/parser/proto-parser-expr.lisp b/src/parser/proto-parser-expr.lisp
index b2919d6..7fc2609 100644
--- a/src/parser/proto-parser-expr.lisp
+++ b/src/parser/proto-parser-expr.lisp
@@ -36,7 +36,7 @@ (defgeneric push-operator (operator state)
    This should apply existing stacked operators as necessary to obey the
    language's precedence rules."))
 
-(export 'push-vlaue)
+(export 'push-value)
 (defgeneric push-value (value state)
   (:documentation
    "Push VALUE onto the STATE's value stack.
@@ -76,7 +76,19 @@ (defgeneric operator-push-action (left right)
 (export 'expr)
 (defparse expr ((&key (nestedp (gensym "NESTEDP-")))
 		operand binop preop postop)
-  "Parse an expression involving unary and binary operators."
+  "Parse an expression involving unary and binary operators.
+
+   Within the parsers for operands and operators, the variable NESTEDP is
+   bound to a generalized boolean which is true if an unmatched open-
+   parenthesis has been seen.
+
+   The OPERAND parser should produce a value; the various operator parsers
+   (BINOP, PREOP, and POSTOP) should produce objects obeying the `operator'
+   protocol.  The final output of the `expr' parse is the result of
+   evaluating the parsed expression.  (Of course, the definition of
+   `evaluation' here is determined entirely by the methods on
+   `apply-operator', so the final value may be a parse tree, for example.)"
+
   (flet ((wrap (parser)
 	   `(parser (,nestedp)
 	      (declare (ignorable ,nestedp))
@@ -106,7 +118,7 @@ (defgeneric operator-right-precedence (operator)
 
    Higher precedence numbers indicate tighter rightward binding.  Under the
    default method for `operator-push-action', a new operator's left
-   precedence may be compared to the existing OPERATOR'S right precedences to
+   precedence may be compared to the existing OPERATOR's right precedences to
    determine the parser's behaviour: if it is higher, then the new operator
    is pushed; otherwise the existing OPERATOR is applied.  Thus, equal
    precedences cause left-associative parsing."))
@@ -206,6 +218,12 @@ (defclass simple-prefix-operator (prefix-operator simple-unary-operator)
 
 (export 'preop)
 (defmacro preop (name (x prec) &body body)
+  "Define a prefix operator.
+
+   The operator will be called NAME in error messages, and have right
+   precedence PREC.  To apply the operator, BODY is evaluated with X bound to
+   the operand."
+
   `(make-instance 'simple-prefix-operator
 		  :name ,name
 		  :precedence ,prec
@@ -213,6 +231,12 @@ (defmacro preop (name (x prec) &body body)
 
 (export 'postop)
 (defmacro postop (name (x prec &key rprec) &body body)
+  "Define a postfix operator.
+
+   The operator will be called NAME in error messages, and have left
+   precedence PREC and right precendence RPREC (defaulting to PREC).  To
+   apply the operator, BODY is evaluated with X bound to the operand."
+
   (once-only (name prec rprec)
     `(make-instance 'simple-postfix-operator
 		    :name ,name
@@ -222,6 +246,14 @@ (defmacro postop (name (x prec &key rprec) &body body)
 
 (export 'binop)
 (defmacro binop (name (x y prec &key rprec (assoc :left)) &body body)
+  "Define a binary operator.
+
+   The operator will be called NAME in error messages, and have left
+   precedence PREC and right precedence RPREC (defaulting to PREC, implying
+   left associativity under the default `operator-push-action'
+   implementation.  To apply the operator, BODY is evaluated with X and Y
+   bound to the operands in the order they were parsed"
+
   (once-only (name prec rprec assoc)
     `(make-instance 'simple-binary-operator
 		    :name ,name