Add Flow control

[inform-resources.git] / informqr / informqr.md

diff --git a/informqr/informqr.md b/informqr/informqr.md
index 8295e07ee3fb04eba88eea131f847cdbffcebb92..0dee485b5c00a62d14ecad8965da1b0872ff52b8 100644 (file)
--- a/informqr/informqr.md
+++ b/informqr/informqr.md
@@ -259,4 +259,132 @@ To return the adjacent child of an object's parent (or nothing):
 
 To return the number of child objects directly below an object:
 
-    children(object)
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+    children(object)
+
+Message passing
+---------------
+
+To a class:
+
+    class.remaining()
+    class.create()
+    class.destroy(object)
+    class.recreate(object)
+    class.copy(to_object,from_object)
+
+To an object:
+
+    object.property(a1,a2, ... a7)
+
+To a routine:
+
+    routine.call(a1,a2, ... a7)
+
+To a string:
+
+    string.print()
+    string.print_to_array(array)
+
+Statements
+----------
+
+Each *statement* is terminated by a semi-colon ";".
+
+A *statement_block* is a single *statement* or a series of 
+*statements* enclosed in braces {...}.
+
+An exclamation "!" starts a comment - rest of line ignored.
+
+A common statement is the assignment:
+
+    variable = expr ;
+
+There are two forms of multiple assignment:
+
+    variable = variable = ... = expr ;
+    variable = expr, variable = expr, ... ;
+
+Routines
+--------
+
+A routine can have up to 15 local variables: word values which are
+private to the routine and which by default are set to zero on each
+call. Recursion is permitted.
+
+A **standalone** routine:
+
+-   has a name, by which it is called using `routine();` can also be
+    called indirectly using
+
+    indirect(routine,a1,a2, ... a7)
+
+-   can take arguments, using `routine(a1,a2, ... a7)`, whose values
+    initialise the equivalent local variables
+
+-   returns true at the final "]"
+
+        [ routine
+            local_var local_var ... local_var ;
+            statement;
+            statement;
+            ...
+            statement;
+            ]
+
+A routine **embedded** as the value of an object property:
+
+-   has no name, and is called when the property is invoked; can also
+    be called explicitly using object.property()
+
+-   accepts arguments only when called explicitly
+
+-   returns false at the final "]"
+
+        property [
+            local_var local_var ... local_var;
+            statement;
+            statement;
+            ...
+            statement;
+            ]
+
+Routines return a single value, when execution reaches the final "\]"
+or an explicit return statement:
+
+    return expr;
+    return;
+    rtrue;
+    rfalse;
+
+To define a dummy standalone routine with N local variables (unless it
+already exists):
+
+    Stub routine N;
+
+Flow control
+------------
+
+To execute statements if *expr* is true; optionally, to execute other
+statements if *expr* is false:
+
+    if (expr)
+        statement_block
+    if (expr)
+        statement_block
+    else
+        statement_block
+
+To execute statements depending on the value of *expr*:
+
+    switch (expr) {
+        value: statement; ... statement;
+        value: statement; ... statement;
+        ...
+        default: statement; ... statement;
+        }
+
+where each *value* can be given as:
+
+    constant
+    lo_constant to hi_constant
+    constant,constant, ... constant
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