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improve docs on if syntax. fixes #81

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Irmen de Jong 2022-10-19 23:53:15 +02:00
parent 53b0b562e6
commit 733c17ad3a
2 changed files with 27 additions and 13 deletions
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26
docs/source/programming.rst
View File

@ -514,16 +514,26 @@ if statements
Conditional execution means that the flow of execution changes based on certiain conditions,
rather than having fixed gotos or subroutine calls::
if aa>4 goto overflow
if xx==5 {
yy = 99
zz = 42
} else {
aa = 3
bb = 9
}
if xx==3 yy = 4
if xx==3 yy = 4 else aa = 2
if xx==5
yy = 42
else if xx==6
yy = 43
else
yy = 44
if xx==5 {
yy = 99
} else {
aa = 3
}
if aa>4 goto some_label
if xx==3 yy = 4
if xx==3 yy = 4 else aa = 2
Conditional jumps (``if condition goto label``) are compiled using 6502's branching instructions (such as ``bne`` and ``bcc``) so

14
docs/source/syntaxreference.rst
View File

@ -783,19 +783,23 @@ Note: to do an indirect *JSR* to a routine with a varying address, you can use t
(which is not very efficient) or you have to write a small piece of inline assembly.
Conditional execution
^^^^^^^^^^^^^^^^^^^^^
if statements
^^^^^^^^^^^^^
With the 'if' / 'else' statement you can execute code depending on the value of a condition::
if <expression> <statements> [else <statements> ]
where <statements> can be just a single statement for instance just a ``goto``, or it can be a block such as this::
If <statements> is just a single statement, for instance just a ``goto`` or a single assignment,
it's possible to just write the statement without any curly braces.
However if <statements> is a block of multiple statements, you'll have to enclose it in curly braces::
if <expression> {
<statements>
} else if <expression> {
<statements>
} else {
<alternative statements>
<statements>
}
@ -807,7 +811,7 @@ itself defines on what status register bit it should branch on::
if_XX <statements> [else <statements> ]
where <statements> can be just a single statement for instance just a ``goto``, or it can be a block such as this::
where <statements> can be just a single statement or a block again::
if_XX {
<statements>