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implement lazy boolean OR and AND operators, || and && respectively

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Sami Samhuri 2010-02-14 23:15:38 -08:00
parent f7e44b7472
commit 9b5c3b795e
1 changed files with 48 additions and 24 deletions
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72
compiler.rb
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@ -264,39 +264,63 @@ class Compiler
# boolean expressions #
#######################
def op(name)
asm.push(EAX)
expected(name) unless match_word(name)
yield
asm.add(ESP, 4)
end
def boolean_expression
boolean_term
while @look == '|'
op '||' do
boolean_term
# !!! this method has moved, IMPLEMENT THIS!
emit("<logical or>")
end
scan
expected('||') unless match_word('||')
false_label = asm.mklabel(:false)
truthy_label = asm.mklabel(:truthy)
done_label = asm.mklabel(:done)
asm.cmp(EAX, FALSE)
asm.jne(truthy_label)
boolean_term
asm.cmp(EAX, FALSE)
asm.je(false_label)
asm.deflabel(truthy_label)
asm.mov(EAX, TRUE)
asm.jmp(done_label)
asm.deflabel(false_label)
asm.mov(EAX, FALSE)
asm.deflabel(done_label)
end
end
def boolean_term
not_factor
while @look == '&'
op '&&' do
not_factor
# !!! this method has moved, IMPLEMENT THIS!
emit("<logical and>")
end
scan
expected('&&') unless match_word('&&')
false_label = asm.mklabel(:false)
done_label = asm.mklabel(:done)
asm.cmp(EAX, FALSE)
asm.je(false_label)
not_factor
asm.cmp(EAX, FALSE)
asm.je(false_label)
asm.mov(EAX, TRUE)
asm.jmp(done_label)
asm.deflabel(false_label)
asm.mov(EAX, TRUE)
asm.deflabel(done_label)
end
end
def boolean_factor
if boolean?(@look)
if get_boolean == 'true'
asm.mov(EAX, -1)
asm.mov(EAX, TRUE)
else
asm.xor(EAX, EAX)
end
@ -321,9 +345,9 @@ class Compiler
# semantically equivalent to !!reg in C or Ruby.
def make_boolean(reg=EAX)
end_label = asm.mklabel(:endmakebool)
asm.cmp(reg, 0) # if false do nothing
asm.cmp(reg, FALSE) # if false do nothing
asm.jz(end_label)
asm.mov(reg, -1) # truthy, make it true
asm.mov(reg, TRUE) # truthy, make it true
asm.deflabel(end_label)
end
@ -389,13 +413,13 @@ class Compiler
asm.cmp(a, b)
asm.jl(true_label)
asm.xor(EAX, EAX) # return false
asm.not_(EAX) if invert # (or true if inverted)
asm.mov(EAX, FALSE) # return false
asm.not_(EAX) if invert # (or true if inverted)
asm.jmp(end_label)
asm.deflabel(true_label)
asm.xor(EAX, EAX) # return true
asm.not_(EAX) unless invert # (or false if inverted)
asm.mov(EAX, FALSE) # return true
asm.not_(EAX) unless invert # (or false if inverted)
asm.deflabel(end_label)
end