scraps.woof

@(load_module 'prelude.woof').

define: 'try:catch:' over: #(Block,Block) as: [|tryBlock, catchBlock|
    withCC: [|cc|
	handler := [ |error| 
	    removeExceptionHandler: handler.
	    do: cc with: #(do: catchBlock with: #(error))
	].
	installExceptionHandler: handler.
	do: tryBlock
    ]
].

define: 'installExceptionHandler:' over: #(Block) as: [ |block|
    $exceptionHandlers := concat: #(block) and: $exceptionHandlers
].

define: 'removeExceptionHandler:' over: #(Block) as: [ |block|
    $exceptionHandlers := drop: 1 from: $exceptionHandlers
].

define: 'throw:' over: #(Error) as: [|error| 
    if: (firstOf: $exceptionHandlers)
    do: [|handler| do: handler with: #(error)]
    else: []
].

define: 'withCC:' over: #(Block) as: [|block|
    @(with_cc block)
].

define: 'do:with:' over: #(Continuation, Nil) as: [|cc, val|
    @(return_cc cc, val)
]


" 


TODO: continuation needs to become a real woof-object, 
with class and everything, so we can dispatch on them (as above)

@(with_cc block) will compile to code like:
----
(SAVE 4) Put the return addr on the stack
(CC 3) ;; Put a fresh continuation on the stack
(LVAR x) ;; Put the block on the stack
(CALLJ) ;; Call the block with continuation as argument
(HALT)
-----

@(return_cc cc, val) will compile to code like:
----
(LVAR x) Put val on the stack
(LVAR y) Put cc on the stack
(RETCC) ;; Pop the continuation, restore the environment & stack, only val remains on the stack
(HALT)
-----

"