From 6b7f8e61c832c7e3364591bafacacc12d088eb24 Mon Sep 17 00:00:00 2001 From: David Schmenk Date: Fri, 4 Jul 2014 20:13:05 -0700 Subject: [PATCH 1/2] Update README.md --- README.md | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/README.md b/README.md index fe419d3..6a45680 100644 --- a/README.md +++ b/README.md @@ -272,26 +272,33 @@ Control structures affect the flow of control through the program. There are co fin ``` -The when/is/otherwise/wend statement is similar to the if/elsif/else/fin construct except that it is more efficient. It selects one path based on the evaluated expressions, then merges the code path back together at the end. However only the 'when' value is compared against a list of expressions. The expressions do not need to be constants, they can be any valid expression. The list of expressions is evaluated in order, so for efficiency sake, place the most common cases earlier in the list. +The when/is/otherwise/wend statement is similar to the if/elsif/else/fin construct except that it is more efficient. It selects one path based on the evaluated expressions, then merges the code path back together at the end. However only the 'when' value is compared against a list of expressions. The expressions do not need to be constants, they can be any valid expression. The list of expressions is evaluated in order, so for efficiency sake, place the most common cases earlier in the list. Just as in C programs, a 'break' statement is required to keep one clause from falling through to the next. Falling through from one clause to the next can have it's uses, so this behavior has been added to PLASMA. ``` when keypressed is keyarrowup cursup + break is keyarrowdown cursdown + break is keyarrowleft cursleft + break is keyarrowright cursright + break is keyctrlx cutline + break is keyctrlv pasteline + break is keyescape cursoff cmdmode redraw + break otherwise bell wend From 5e8c9282e4d66474601dab8ede9de7e36f5eabac Mon Sep 17 00:00:00 2001 From: David Schmenk Date: Fri, 4 Jul 2014 20:43:02 -0700 Subject: [PATCH 2/2] Update 'pointer-to' operator and 'when' statement --- doc/User Manual.md | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/doc/User Manual.md b/doc/User Manual.md index 9240c3c..dbeb211 100644 --- a/doc/User Manual.md +++ b/doc/User Manual.md @@ -269,6 +269,28 @@ def strlen(strptr) return ^strptr end ``` +Pointers to structures or arrays can be referenced with the `->` and `=>` operators, pointing to `byte` or `word` sized elements. +``` +const elem_id = 0 +const elem_addr = 1 + +def addentry(entry, id, addr) + entry->elem_id = id ; set ID byte + entry=>elem_addr = addr ; set address + return entry + 3 ; return next enry address +end +``` +The above is equivalent to: +``` +const elem_id = 0 +const elem_addr = 1 + +def addentry(entry, id, addr) + (entry).elem_id = id ; set ID byte + (entry):elem_addr = addr ; set address + return entry + 3 ; return next enry address +end +``` ##### Addresses of Data/Code Along with dereferencing a pointer, there is the question of getting the address of a variable. The `@` operator prepended to a variable name or a function definition name, will return the address of the variable/definition. From the previous example, the call to `strlen` would look like: @@ -403,13 +425,16 @@ The complex test case is handled with `when`. Basically a `if`, `elsifF`, `else` when key is 'A' ; handle A character + break is 'B' ; handle B character + break ``` ... ``` is 'Z' ; handle Z character + break otherwise ; Not a known key wend @@ -424,13 +449,15 @@ byte a when TRUE is (a <= 10) ; 10 or less + break is (a > 10) AND (a < 20) ; between 10 and 20 + break is (a >= 20) ; 20 or greater wend ``` - +A `when` clause can fall-through to the following clause, just like C `switch` statements by leaving out the `break` at ##### FOR \ [STEP]/NEXT Iteration over a range is handled with the `for`/`next` loop. When iterating from a smaller to larger value, the `to` construct is used; when iterating from larger to smaller, the `downto` construct is used. ```