CS 330 Lecture 13 – Functions
Agenda
- what ?s
- adding functions to Logo
- scope choices
- closures in other languages
TODO
- For an extra credit quarter sheet, write a Logo program. Clone the repository of our code in Eclipse, run
Interpreter, and feed it a file containing a Logo program. Share your program on Piazza.
Note
Today we will round out our discussion of crafting our own programming languages by adding functions to Logo. We will encounter the problem that all language designers encounter. How do I handle scope when executing a function? We’ll examine a few different options, but ultimately settle on closures.
Code
Logo.g
grammar Logo;
// Nonterminals
program
: block EOF
;
block
: (statement? NEWLINE)*
;
statement
: REPEAT expression NEWLINE block END # Repeat
| PRINT expression # Print
| IF expression NEWLINE block ELSE NEWLINE block END # If
| MOVE expression # Move
| TURN expression # Turn
| IDENTIFIER ASSIGNMENT expression # Assignment
| TO IDENTIFIER (IDENTIFIER (COMMA IDENTIFIER)*)? NEWLINE block END # FunctionDefinition
| IDENTIFIER (expression (COMMA expression)*)? # FunctionCall
;
expression
: INTEGER # Integer
| IDENTIFIER # Identifier
| expression op=(MULTIPLY|DIVIDE|MOD) expression # Multiplicative
| expression op=(PLUS|MINUS) expression # Additive
;
// Terminals
IF: 'if';
ELSE: 'else';
TO: 'to';
MOVE: 'move';
TURN: 'turn';
REPEAT: 'repeat';
END: 'end';
PRINT: 'print';
LEFT_PARENTHESIS: '(';
RIGHT_PARENTHESIS: ')';
MULTIPLY: '*';
DIVIDE: '/';
MOD: '%';
PLUS: '+';
COMMA: ',';
MINUS: '-';
ASSIGNMENT: '=';
IDENTIFIER: [a-zA-Z]+ [a-zA-Z_]*;
INTEGER: '-'? [0-9]+;
NEWLINE: '\n';
WHITESPACE: [ \t]+ -> skip;
makefile
Note to copy and pasters: makefile rules need to be indented with real tabs, not spaces.
ANTLR_JAR = ${HOME}/bin/antlr-4.5.2-complete.jar
Interpreter.class: LogoLexer.class LogoParser.class Block.class Expression.class ExpressionInteger.class ExpressionPlus.class ExpressionMinus.class ExpressionMultiply.class ExpressionDivide.class ExpressionMod.class Statement.class StatementRepeat.class StatementPrint.class StatementIf.class StatementMove.class StatementTurn.class Environment.class ExpressionIdentifier.class StatementAssignment.class StatementFunctionDefinition.class StatementFunctionCall.class LogoVirtualMachine.java
LogoLexer.java LogoParser.java: Logo.g
java -cp ${ANTLR_JAR} org.antlr.v4.Tool Logo.g
%.class: %.java
javac -cp ${ANTLR_JAR}:. $<
run:
java -cp ${ANTLR_JAR}:. Interpreter
clean:
rm -rf *.class LogoLexer.java LogoParser.java LogoBaseListener.java LogoListener.java *.tokens
Interpreter.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
LogoVirtualMachine.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
Block.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
Environment.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
Expression.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
ExpressionDivide.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
ExpressionIdentifier.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
ExpressionInteger.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
ExpressionMinus.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
ExpressionMod.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
ExpressionMultiply.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
ExpressionPlus.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
Statement.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementAssignment.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementFunctionCall.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementFunctionDefinition.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementIf.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementListener.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementMove.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementPrint.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementRepeat.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
StatementTurn.java
/usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:315:in `to_specs': Could not find 'coderay' (>= 0) among 94 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/var/www/.local/share/gem/ruby/3.2.0:/var/lib/gems/3.2.0:/usr/local/lib/ruby/gems/3.2.0:/usr/lib/ruby/gems/3.2.0:/usr/lib/x86_64-linux-gnu/ruby/gems/3.2.0:/usr/share/rubygems-integration/3.2.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/3.2.0:/home/johnch/.gems' , execute `gem env` for more information from /usr/lib/ruby/vendor_ruby/rubygems/dependency.rb:327:in `to_spec' from /usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_gem.rb:57:in `gem' from ./coderay:24:in `'
square.logo
to square length
repeat 4
move length
turn 90
end
end
square 100
square 100
square 100
square 100
squares.logo
length = 100
repeat 99
move length
turn 90
move length
turn 90
move length
turn 90
move length
length = length - 1
end
scopes.logo
i = 17
print i
to foo
i = 39
print i
end
foo
print i