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authorKarl Berry <karl@freefriends.org>2009-08-15 23:57:48 +0000
committerKarl Berry <karl@freefriends.org>2009-08-15 23:57:48 +0000
commit16d128e5e10d541a78654b86409d5a3539f07708 (patch)
tree66de0af63c3811bb3040c16e9b52c11985f70811 /Build/source/utils/asymptote/virtualfieldaccess.h
parentb20f78c549859ec0e8610bdd3ad904245e86b489 (diff)
asymptote 1.83
git-svn-id: svn://tug.org/texlive/trunk@14696 c570f23f-e606-0410-a88d-b1316a301751
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+/*****
+ * virtualfieldaccess.h
+ * Andy Hammerlindl 2009/07/23
+ *
+ * Implements the access subclass used to read and write virtual fields.
+ *****/
+
+#include "access.h"
+
+namespace trans {
+// In code such as
+// pair z; write(z.x);
+// to evaluate the expression z.x, first z is pushed onto the stack, then as
+// it is not a record, instead of accessing its field in the usual way for a
+// record, a builtin function is called which pops z off the stack and
+// replaces it with z.x. virtualFieldAccess provides the access for the
+// virtualField 'x', and 'getter' is the access to the builtin function which
+// replaces z with z.x.
+//
+// If the virtual field z.x were mutable, then setter would access a builtin
+// function, which pops a real number and then z off of the stack, sets the
+// z.x to that new value, and puts the value back on the stack. In this case,
+// pairs are immutable, but other virtual fields may not be.
+class virtualFieldAccess : public access {
+ access *getter;
+ access *setter;
+
+ // As an optimization could add a 'caller' field, to handle calls to
+ // functions such as 'a.push(x)' where a is an array more efficiently.
+public:
+ virtualFieldAccess(access *getter, access *setter = 0)
+ : getter(getter), setter(setter) {}
+
+ virtualFieldAccess(vm::bltin getter, vm::bltin setter = 0)
+ : getter(new bltinAccess(getter)),
+ setter(setter ? new bltinAccess(setter) : 0) {}
+
+ void encode(action act, position pos, coder &e);
+ void encode(action act, position pos, coder &e, frame *);
+
+ // Attempting to WRITE a read-only field will give an error, but if the
+ // error is caught at a higher level, a better error message (including the
+ // name of the field) can be given. This function allows such handling.
+ bool readonly() {
+ return (bool)setter;
+ }
+};
+
+} // namespace trans