Entering Programs

Programs start with two opening angle brackets (<<) and end with two closing angle brackets (>>). Elements of a program can be of any type including other programs. Elements are separated by spaces.

Examples: << 2 * >>, << << 2 * >> << 3 * >> ifte >>

You can store a program in a variable and execute it by typing the name of the variable without the single quotes.

You can use the following programming structures in programs:

->Create local variables and use them in the following program

Usage:obj₁ obj₂ ... obj_n -> v₁ v₂ ... v_n << ... >>

do-until-endIndefinite loop that gets executed at least once

Usage:do commands until condition end

for-nextDefinite loop incremented by one

Usage:begin end for index commands next

for-stepDefinite loop with a specified increment

Usage:begin end for index commands increment step

if-then-[else]-endConditional structure

Usage:if condition then true-commands end

if condition then true-commands else false-commands end

iferr-then-[else]-endError trapping conditional structure

Usage:iferr commands then error-commands end

iferr commands then error-commands else no-error-commands end

start-nextDefinite loop that gets executed at least once and is incremented by one

Usage:begin end start commands next

start-stepDefinite loop with a specified increment that gets executed at least once

Usage:begin end start commands increment step

while-repeat-endIndefinite loop

Usage:while condition repeat commands end

Do not use i (square-root of negative one) or any other built-in command for local variables or loop indices.