ELSE operator

[vooon]

The else statement extremely necessary.

Example syntax:

IF stmt {
 run foo.
}
ELSE {
 run bar.
}

IF stmt {
 run foo.
}
ELSE IF stmt2 {
 run baz.
}

[Dunbaratu]

I'd second this. I've had to write weird code at times because of the lack of an else.

[erendrake]

We have two operators here ELSE and ELSE IF. Which is more important to you so we can prioritize?

[vooon]

I think only ELSE. With proper implementation ELSE IF is obtained automatically.

In terms of kRISC.tpg:

ELSE -> @"else";
if_else_stmt -> IF expr instruction_block ELSE instruction_block EOI?;

[marianoapp]

That's right, but the ELSE part in the grammar should be optional, like this:

if_stmt -> IF expr instruction_block (ELSE instruction_block)? EOI?;

[Dunbaratu]

I've implemented the ELSE in my own local copy, but I don't understand how to push two different separate pull requests to github that are both pending at the same time. It keeps trying to merge my changes for this issue with my previous pull request for a different issue. Do I need to make a branch to keep that from happening? All my past experience has been with SVN and CVS so I don't quite 'get' Github yet.

At any rate, if I can figure out how to get my code into a second pull request, I have this solved so that the following test script works correctly:

//KOS
//  A script with the purpose of testing that 'if' and 'else' work right:

set a to 10.
set b to 20.
set c to 40.

print "IF,  one line body, true check:".
print "is " + a + " = 10?".
if a = 10
  print "  yes.".
print "IF,  one line body, false check:".
print "is " + b + " = 10?".
if b = 10
  print "  yes.".

print "IF,  two line body requiring braces:".
print "is " + a + " = 10?".
if a = 10 {
  print "  yes.".
  set doNothing to 1. // just to make a reason for the braces.
}.

print "if/else, one-liners, true check:".
print "is " + a + " = 10?".
if a = 10
  print "  yes".
else
  print "  no".

print "if/else, one-liners, false check:".
print "is " + b + " = 10?".
if b = 10
  print "  yes".
else
  print "  no".

print "if/else, multi-line bodies, true check:".
print "is " + a + " = 10?".
if a = 10 {
  print "  yes".
  set doNothing to 1. // just to make the body longer than 1 stmt.
} else {
  print "  no".
  set doNothing to 1. // just to make the body longer than 1 stmt.
}.

print "if/else, multi-line bodies, false check:".
print "is " + b + " = 10?".
if b = 10 {
  print "  yes".
  set doNothing to 1. // just to make the body longer than 1 stmt.
} else {
  print "  no".
  set doNothing to 1. // just to make the body longer than 1 stmt.
}.

print "nested if/else, one-liners, hits first term:".
print "what is " + a + " ?".
if a < 15
  print "  less than 15".
else if a < 20
  print "  in the range [15,20)".
else if a < 30
  print "  in the range [20,30}".
else 
  print "  >= 30".

print "nested if/else, one-liners, hits third term:".
print "what is " + b + " ?".
if b < 15
  print "  less than 15".
else if b < 20
  print "  in the range [15,20)".
else if b < 30
  print "  in the range [20,30}".
else 
  print "  >= 30".

print "nested if/else, one-liners, hits final else:".
print "what is " + c + " ?".
if c < 15
  print "  less than 15".
else if c < 20
  print "  in the range [15,20)".
else if c < 30
  print "  in the range [20,30}".
else 
  print "  >= 30".

print "nested if/else, mix of one-line and braces, hits middle term:".
print "what is " + b + " ?".
if b < 10
  print "  less than 10.".
else if b < 30 {
  print "  in the range [10,30}".
  set doNothing to 1. // pointless line to force need for braces.
} else {
  print "  >= 30".
  set doNothing to 1. // pointless line to force need for braces.
}.

I have to say, @marianoapp, the kRISC code is nice and easy to understand (provided you know a few basic things about what assembly language programs typically look like) and I'm impressed with the internals now that I've dived into them a bit to make this work. The ELSE implementation worked right on the first attempt without headaches, just from basic guesswork on my part about how to implement it, looking at how the else-less if worked already.

[marianoapp]

Thanks, I appreciate it.
Closing this as it was implemented along the fix for #20.