How to run

REPL (Read-Eval-Print Loop)

$ java lang.Main

Code from a file

$ java lang.Main <filename>

Features

Comments

(this will be ignored) 1 print
( Output:
1.0
)

(even ( nested ) parens will ( be (ignored))) 1 print
( Output:
1.0
)

Basic arithmetics

1 2 + print
( Output:
3.0
)

If conditions

if 1 2 < do
    1 print
end
( Output:
1.0
)

if 1 2 > do
    1 print
end
( Output:
)

if 1 2 < do
    1 print
else
    2 print
end
( Output:
1.0
)

if 1 2 > do
    1 print
else
    2 print
end
( Output:
2.0
)

While loops

5
while 1dup 0 > do
    1dup print
    1 -
end
1drop
( Output:
5.0
4.0
3.0
2.0
1.0
)

Functions

Notation

a, b -> c, d

• The stack is expected to have two values, a and b, on top where b is on top of a.
• After the function is finished, the stack will have two values, c and d, on top where d is on top of c.

Standard functionality

Stack manipulation

• <n>dup: Duplicates the top n values from the stack (e.g. 2dup duplicates the top 2 values) (a1, a2, ..., an -> a1, a2, ..., an, a1, a2, ..., an)
• <n>drop: Removes the top n values from the stack and discards them (e.g. 2drop discards the top 2 values) (a1, a2, ..., an ->)
• reverse: Reverses the whole stack (a, b, ..., x -> x, ..., b, a)
• <n>reverse: Reverses the top n values from the stack (e.g. 3reverse reverses the top 3 values) (a1, a2, ..., an -> an, ..., a2, a1)
• <m>swap<n>: Swaps the top n values and the next m elements (e.g. 2swap2 performs a, b, c, d -> c, d, a, b) (a1, a2, ..., am, b1, b2, ..., bn -> b1, b2, ..., bn, a1, a2, ..., am)
• <m>over<n>: Copies the next m elements over the top n elements (e.g. 2over2 performs a, b, c, d -> a, b, c, d, a, b) (a1, a2, ..., am, b1, b2, ..., bn -> a1, a2, ..., am, b1, b2, ..., bn, a1, a2, ..., am)

Arithmetics

• +: Sums the top 2 values from the stack and pushes the result back (a, b -> a + b)
• -: Subtracts the top 2 values from the stack and pushes the result back (a, b -> a - b)
• *: Multiplies the top 2 values from the stack and pushes the result back (a, b -> a * b)
• /: Divides the top 2 values from the stack and pushes the result back (a, b -> a / b)
• %: Computes the top value modulo the second from the top value and pushes the result back (a, b -> a % b)
• divmod: A combination of / and % (a, b -> a / b, a % b)
• pow: Computes the value of the second from the top value to the power of the top value and pushes the result back (a, b -> pow(a, b))
• sqrt: Computes the square root of the number on top and pushes the result back (a -> sqrt(a))

Trigonometry

• sin: Calculates the sine of the top value of the stack and pushes the result back (a -> sin(a))
• cos: Calculates the cosine of the top value of the stack and pushes the result back (a -> cos(a))

Comparisons

• <: Compares the top two values and pushes 1 if the top value is bigger, otherwise pushes 0 (a, b -> a < b)
• <: Compares the top two values and pushes 1 if the top value is smaller, otherwise pushes 0 (a, b -> a > b)

Debugging

• print: Prints the top value from the stack and discards it (a --)

To Do list

Functions/procedures

fn add + end
1 2 add

Other data types

"Hello, World" print

Type checks

1 + (should raise an error before the code is run)

• Figure syntax for function definitions
• Figure how to make sure ifs and whiles don't alter the stack